Assembly with piezoelectric layer with embedded interdigital transducer electrode

ABSTRACT

An acoustic wave device assembly is disclosed. The acoustic wave device assembly can include a first acoustic wave device that includes a first substrate, a first piezoelectric layer, a first solid acoustic mirror that is disposed between the first substrate and the first piezoelectric layer, and a first interdigital transducer electrode that is embedded in the piezoelectric layer. The acoustic wave device assembly can include a second acoustic wave device that includes a second substrate, a second piezoelectric layer, a second solid acoustic mirror that is disposed between the second substrate and the second piezoelectric layer, and a second interdigital transducer electrode that is in contact with the second piezoelectric layer. The second acoustic wave device is stacked over the first acoustic wave device. The first acoustic wave device and the second acoustic wave device are spaced by a spacer assembly such that a cavity is formed between the first acoustic wave device and the second acoustic wave device.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication, including U.S. Provisional Patent Application No.63/251,982, filed Oct. 4, 2021, titled “STACKED ACOUSTIC WAVE DEVICEASSEMBLY,” are hereby incorporated by reference under 37 CFR 1.57 intheir entirety.

BACKGROUND Technical Field

Embodiments of the invention relate to stacked acoustic wave deviceassemblies.

Description of the Related Technology

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed. In BAW resonators, acoustic waves propagate in a bulk of apiezoelectric layer. Example BAW resonators include film bulk acousticwave resonators (FBARs) and solidly mounted resonators (SMRs). Certainacoustic resonators can include features of SAW resonators and featuresof BAW resonators. A stacked acoustic wave device assembly can include aplurality of acoustic wave devices (or: acoustic wave resonators).

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan be a band pass filter. A plurality of acoustic wave filters can bearranged as a multiplexer. For example, two acoustic wave filters can bearranged as a duplexer. The two acoustic wave filters of a duplexer canbe included in one stacked acoustic wave device assembly. As anotherexample, four acoustic wave filters can be arranged as a quadplexer, forexample four acoustic wave filters provided by the two acoustic filterdevices of each of two stacked acoustic wave devices assemblies.

SUMMARY

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

A stacked acoustic wave device assembly is disclosed. The stackedacoustic wave device assembly can include a first acoustic wave devicethat includes a first substrate, a first piezoelectric layer, a firstsolid acoustic mirror disposed between the first substrate and the firstpiezoelectric layer, and a first interdigital transducer electrode incontact with the first piezoelectric layer. The stacked acoustic wavedevice assembly can include a second acoustic wave device that includesa second substrate, a second piezoelectric layer, a second solidacoustic mirror disposed between the second substrate and the secondpiezoelectric layer, and a second interdigital transducer electrode incontact with the second piezoelectric layer. The second acoustic wavedevice is stacked over the first acoustic wave device. The firstacoustic wave device and the second acoustic wave device are spaced by aspacer assembly such that a cavity is formed between the first acousticwave device and the second acoustic wave device.

In one embodiment, the first piezoelectric layer has a first side and asecond side opposite the first side. The second piezoelectric layer canbe arranged such that the first side of the first piezoelectric layerfaces the second piezoelectric layer. The first solid acoustic mirrorcan be arranged such that the second side of the first piezoelectriclayer faces the first solid acoustic mirror.

In one embodiment, the first piezoelectric layer is arranged at a firstside of the second piezoelectric layer and the second solid acousticmirror is arranged at a second side of the second piezoelectric layeropposite to the first side of the second piezoelectric layer.

In one embodiment, the first interdigital transducer electrode and thesecond interdigital transducer electrode face each other in the cavity.

In one embodiment, the first solid acoustic mirror, the firstpiezoelectric layer, the first interdigital transducer electrode, thesecond interdigital transducer electrode, the spacer assembly, thesecond piezoelectric layer, and the second solid acoustic mirror arepositioned between the first substrate and the second substrate.

In one embodiment, at least one of the first acoustic wave device or thesecond acoustic wave device is a laterally excited bulk acoustic waveresonator, and includes lithium niobate having a crystal orientation of(α, β, γ), with α between −10° and +10°, β between −10° and +10°, and γbetween 80° and 100° in Euler angles.

In one embodiment, at least one of the first acoustic wave device or thesecond acoustic wave device is a leaky longitudinal surface acousticwave resonator, and includes lithium niobate having a crystalorientation of (α,β, γ), with α between 80° and 100°, β between 80° and100°, and γ between 30° and 50°.

In one embodiment, the first interdigital transducer electrode disposedover the first piezoelectric layer and in the cavity.

In one embodiment, the second interdigital transducer electrode disposedover the second piezoelectric layer and in the cavity.

In one embodiment, the spacer assembly includes a plurality of columnsthat are in contact with both the first acoustic wave device and thesecond acoustic wave device. The columns can include gold or copper.

In one embodiment, the solid acoustic mirror structure includesalternating low impedance layers and high impedance layer that has ahigher impedance than the low impedance layer.

In one embodiment, the first acoustic wave device has a single mirrorstructure and the second acoustic wave device has a double mirrorstructure.

In one embodiment, the first wave device further includes a passivationlayer over the first interdigital transducer electrode.

In one embodiment, the first interdigital transducer electrode isdisposed on the first piezoelectric layer.

In one embodiment, the second substrate and the second solid acousticmirror are positioned between the first and second piezoelectric layers.

In one aspect, a radio frequency module is disclosed. The radiofrequency module can include a first acoustic wave device that includesa first solid acoustic mirror on a first substrate, a firstpiezoelectric layer over the first solid acoustic mirror, and a firstinterdigital transducer electrode in contact with the firstpiezoelectric layer. The radio frequency module can include a radiofrequency circuit element that is coupled to the first acoustic wavedevice, and a second acoustic wave device that includes a second solidacoustic mirror on a second substrate, a second piezoelectric layer overthe second solid acoustic mirror, and a second interdigital transducerelectrode in contact with the second piezoelectric layer. The firstacoustic wave device, the second acoustic wave device, and the radiofrequency circuit element are enclosed within a common package, and thefirst acoustic wave device and the second acoustic wave device arestacked with a spacer assembly therebetween such that a cavity is formedbetween the first acoustic wave device and the second acoustic wavedevice.

In one embodiment, the radio frequency circuit element is a radiofrequency amplifier arranged to amplify a radio frequency signal, andthe radio frequency circuit element is a first switch configured toselectively couple the first acoustic wave device to an antenna port ofthe first radio frequency module.

In one aspect, a wireless communication device is disclosed. Thewireless communication device can include a first acoustic wave devicethat includes a first solid acoustic mirror over a first substrate, afirst piezoelectric layer over the first solid acoustic mirror, and afirst interdigital transducer electrode in contact with the firstpiezoelectric layer. The wireless communication device can include asecond acoustic wave device including a second solid acoustic mirrorover a second substrate, a second piezoelectric layer over the secondsolid acoustic mirror, and a second interdigital transducer electrode incontact with the second piezoelectric layer. The wireless communicationdevice can include an antenna that is coupled to the first acoustic wavedevice and the second acoustic wave device, a radio frequency amplifierthat is coupled to the first acoustic wave device and configured toamplify a radio frequency signal, and a transceiver in communicationwith the radio frequency amplifier. The first acoustic wave device andthe second acoustic wave device are stacked with a spacer assemblytherebetween such that a cavity is formed between the first acousticwave device and the second acoustic wave device.

In one embodiment, the wireless communication device further includes abaseband processor in communication with the transceiver.

In one aspect, an acoustic wave device assembly is disclosed. Theacoustic wave device assembly can include a first interdigitaltransducer electrode in contact with a first piezoelectric layer, asecond interdigital transducer electrode in contact with a secondpiezoelectric layer, and an acoustic mirror structure that is positionedbetween the first interdigital transducer electrode and the secondinterdigital transducer electrode. The acoustic mirror structure has afirst portion that is configured to confine acoustic energy of a firstacoustic wave generated by the first interdigital transducer electrode,and a second portion that is configured to confine acoustic energy of asecond acoustic wave generated by the second interdigital transducerelectrode.

In one embodiment, the acoustic mirror structure includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers. The first portion and thesecond portion of the acoustic mirror structure can be spaced by asupport substrate. A first acoustic wave device can include the firstinterdigital transducer electrode, the first piezoelectric layer, thefirst portion of the acoustic mirror structure, and at least a portionof the support substrate. A second acoustic wave device can include thesecond interdigital transducer electrode, the second piezoelectriclayer, the second portion of the acoustic mirror structure, and at leasta portion of the support substrate. The low impedance layers of thefirst portion and the low impedance layers of the second portion canhave different thicknesses. The high impedance layers of the firstportion and the high impedance layers of the second portion can havedifferent thicknesses. The first portion cam at least partially overlapthe second portion.

In one embodiment, the acoustic wave device assembly further includes afirst lid that is coupled to the first acoustic wave device. A firstspacer assembly can be disposed between the first piezoelectric layerand the first lid so as to at least partially define a first cavity. Theacoustic wave device assembly can further include a second lid that iscoupled to the second acoustic wave device. A second spacer assembly canbe disposed between the second piezoelectric layer and the second lid soas to at least partially define a second cavity.

In one embodiment, a wireless communication device includes the acousticwave device assembly and an antenna that is coupled to the acoustic wavedevice assembly.

In one aspect, an acoustic wave device assembly is disclosed. Theacoustic wave device assembly can include a first acoustic wave deviceand a second acoustic wave device. The first acoustic wave deviceincludes a first piezoelectric layer, a first interdigital transducerelectrode in contact with the first piezoelectric layer, and a firstsolid acoustic mirror. The second acoustic wave device includes a secondpiezoelectric layer, a second interdigital transducer electrode incontact with the second piezoelectric layer, and a second solid acousticmirror. The first acoustic wave device and the second acoustic wavedevice are stacked on one another such that the first solid acousticmirror and the second solid acoustic mirror are positioned between thefirst piezoelectric layer and the second piezoelectric layer.

In one embodiment, the first solid acoustic mirror and the second solidacoustic mirror include alternating low impedance layers and highimpedance layers that has a higher impedance than the low impedancelayers. The first acoustic wave device can further include a firstsupport substrate disposed between the first and second solid acousticmirrors. The second acoustic wave device can further include a secondsupport substrate disposed between the first support substrate and thesecond solid acoustic mirror. The low impedance layers of the firstsolid acoustic mirror and the low impedance layers of the second solidacoustic mirror can have different thicknesses. The high impedancelayers of the first solid acoustic mirror and the high impedance layersof the second solid acoustic mirror can have different thicknesses. Thefirst solid acoustic mirror can at least partially overlap the secondsolid acoustic mirror.

In one embodiment, the acoustic wave device assembly further includes afirst lid that is coupled to the first acoustic wave device. A firstspacer assembly can be disposed between the first piezoelectric layerand the first lid so as to at least partially define a first cavity. Theacoustic wave device assembly can further include a second lid that iscoupled to the second acoustic wave device, a second spacer assembly isdisposed between the second piezoelectric layer and the second lid so asto at least partially define a second cavity.

In one embodiment, a wireless communication device includes the acousticwave device assembly and an antenna that is coupled to the acoustic wavedevice assembly.

In one aspect, an acoustic wave device assembly is disclosed. theacoustic wave device assembly can include a first acoustic wave deviceand a second acoustic wave device. The first acoustic wave deviceincludes a first substrate, a first piezoelectric layer, a first solidacoustic mirror disposed between the first substrate and the firstpiezoelectric layer, and a first interdigital transducer electrodehaving a first portion embedded in the first piezoelectric layer and asecond portion disposed over a surface of the first piezoelectric layer.The second acoustic wave device including a second substrate, a secondpiezoelectric layer, a second solid acoustic mirror disposed between thesecond substrate and the second piezoelectric layer, and a secondinterdigital transducer electrode in contact with the secondpiezoelectric layer. The second acoustic wave device is stacked over thefirst acoustic wave device. The first acoustic wave device and thesecond acoustic wave device are spaced by a spacer assembly such that acavity is formed between the first acoustic wave device and the secondacoustic wave device.

In one embodiment, the second interdigital transducer electrode has athird portion embedded in the second piezoelectric layer and a fourthportion disposed over a surface of the second piezoelectric layer. Thesecond portion of the first interdigital transducer electrode and thefourth portion of the second interdigital transducer electrode can bedisposed in the cavity. The first acoustic wave device can furtherinclude a passivation layer over the second portion of the firstinterdigital transducer electrode.

In one embodiment, the first solid acoustic mirror includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers of first solid acoustic mirror.The second solid acoustic mirror can include alternating low impedancelayers and high impedance layers that has a higher impedance than thelow impedance layers of second solid acoustic mirror. The low impedancelayers of the first solid acoustic mirror and the low impedance layersof the second solid acoustic mirror can have different thicknesses.

In one embodiment, the first piezoelectric layer and the secondpiezoelectric layer are positioned between the first and secondsubstrates.

In one embodiment, the second substrate is disposed between the firstand second piezoelectric layers.

In one embodiment, wherein at least one of the first acoustic wavedevice or the second acoustic wave device is a laterally excited bulkacoustic wave resonator.

In one embodiment, at least one of the first acoustic wave device or thesecond acoustic wave device is a leaky longitudinal surface acousticwave resonator.

In one embodiment, the first acoustic wave device has a single mirrorstructure and the second acoustic wave device has a double mirrorstructure.

In one aspect, an acoustic wave device assembly is disclosed. Theacoustic wave device assembly can include a first acoustic wave deviceand a second acoustic wave deice. The first acoustic wave deviceincludes a first substrate, a first piezoelectric layer, a first solidacoustic mirror disposed between the first substrate and the firstpiezoelectric layer, and a first interdigital transducer electrodedisposed over the piezoelectric layer and at least partially embedded inthe first piezoelectric layer. The second acoustic wave device includinga second substrate, a second piezoelectric layer, a second solidacoustic mirror disposed between the second substrate and the secondpiezoelectric layer, and a second interdigital transducer electrode incontact with the second piezoelectric layer. The second acoustic wavedevice is stacked over the first acoustic wave device. The firstacoustic wave device and the second acoustic wave device are spaced by aspacer assembly such that a cavity is formed between the first acousticwave device and the second acoustic wave device.

In one embodiment, the second interdigital transducer electrode is atleast partially embedded in the second piezoelectric layer. The firstacoustic wave device further can include a passivation layer over thesecond portion of the first interdigital transducer electrode.

In one embodiment, the first solid acoustic mirror includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers of first solid acoustic mirror.The second solid acoustic mirror can include alternating low impedancelayers and high impedance layers that has a higher impedance than thelow impedance layers of second solid acoustic mirror, and the lowimpedance layers of the first solid acoustic mirror and the lowimpedance layers of the second solid acoustic mirror have differentthicknesses.

In one embodiment, the first piezoelectric layer and the secondpiezoelectric layer are positioned between the first and secondsubstrates.

In one embodiment, the second substrate is disposed between the firstand second piezoelectric layers.

In one embodiment, the first acoustic wave device has a single mirrorstructure and the second acoustic wave device has a double mirrorstructure.

In one aspect, an acoustic wave device assembly is disclosed. theacoustic wave device assembly can include a first acoustic wave device,a second acoustic wave device, and a spacer assembly. The first acousticwave device including a first substrate, a first piezoelectric layer, afirst solid acoustic mirror disposed between the first substrate and thefirst piezoelectric layer, and a first interdigital transducer electrodein contact with the first piezoelectric layer. The second acoustic wavedevice including a second substrate, a second piezoelectric layer, asecond solid acoustic mirror disposed between the second substrate andthe second piezoelectric layer, a second interdigital transducerelectrode in contact with the second piezoelectric layer, and a thirdsolid acoustic mirror over the second interdigital transducer electrode,the first acoustic wave device and the second acoustic wave device beingstacked on one another. The spacer assembly is disposed over the firstpiezoelectric layer.

In one embodiment, the first interdigital transducer electrode isdisposed over the first piezoelectric layer such that the firstpiezoelectric layer is positioned between the first interdigitaltransducer electrode and the first solid acoustic mirror. The firstacoustic wave device can further include a passivation layer over thefirst interdigital transducer electrode.

In one embodiment, the first interdigital transducer electrode is atleast partially embedded in the first piezoelectric layer.

In one embodiment, the spacer assembly is positioned between the firstand second acoustic wave devices such that a cavity is formed betweenthe first and second acoustic wave devices.

In one embodiment, the second substrate is positioned between the firstpiezoelectric layer and the second solid acoustic mirror.

In one embodiment, the acoustic wave device assembly further includes alid coupled to the spacer assembly. The first substrate and the secondsubstrate can be positioned between the first and second solid acousticmirror. The first substrate can be defined by a first portion of ashared substrate, and second substrate can be defined by a secondportion of the shared substrate.

In one embodiment, the second acoustic wave device further includes athird substrate positioned such that the third solid acoustic mirror ispositioned between the second piezoelectric layer and the thirdsubstrate.

In one embodiment, the first solid acoustic mirror includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers of first solid acoustic mirror.The second solid acoustic mirror can include alternating low impedancelayers and high impedance layers that has a higher impedance than thelow impedance layers of second solid acoustic mirror. The low impedancelayers of the first solid acoustic mirror and the low impedance layersof the second solid acoustic mirror can have different thicknesses.

In one aspect, an acoustic wave device assembly is disclosed. theacoustic wave device assembly can include a first acoustic wave devicethat has a single mirror structure, a second acoustic wave device thathas a double mirror structure, and a spacer assembly. The secondacoustic wave device is stacked on the first acoustic wave device. Thespacer assembly is disposed over the first acoustic wave device and atleast partially defining a cavity.

In one embodiment, the spacer assembly is positioned between the firstand second acoustic wave devices.

In one embodiment, the first acoustic wave device includes a firstsubstrate, a first piezoelectric layer, a first solid acoustic mirrordisposed between the first substrate and the first piezoelectric layer,and a first interdigital transducer electrode in contact with the firstpiezoelectric layer. The second acoustic wave device can include asecond substrate, a second piezoelectric layer, a second solid acousticmirror disposed between the second substrate and the secondpiezoelectric layer, a second interdigital transducer electrode incontact with the second piezoelectric layer, and a third solid acousticmirror over the second interdigital transducer electrode. The firstinterdigital transducer electrode can be disposed over the firstpiezoelectric layer. The first acoustic wave device can further includea passivation layer over the first interdigital transducer electrode.

In one embodiment, the first interdigital transducer electrode isembedded in the first piezoelectric layer.

In one aspect, an acoustic wave device assembly is disclosed. Theacoustic wave device assembly can include a first acoustic wave deviceand a second acoustic wave device. The first acoustic wave deviceincludes a first substrate, a first piezoelectric layer, a first solidacoustic mirror disposed between the first substrate and the firstpiezoelectric layer, and a first interdigital transducer electrodeembedded in the piezoelectric layer. The second acoustic wave deviceincludes a second substrate, a second piezoelectric layer, a secondsolid acoustic mirror disposed between the second substrate and thesecond piezoelectric layer, and a second interdigital transducerelectrode in contact with the second piezoelectric layer. The secondacoustic wave device is stacked over the first acoustic wave device. Thefirst acoustic wave device and the second acoustic wave device arespaced by a spacer assembly such that a cavity is formed between thefirst acoustic wave device and the second acoustic wave device.

In one embodiment, the second interdigital transducer is embedded in thesecond piezoelectric layer.

In one embodiment, the first interdigital transducer electrode iscompletely embedded in the first piezoelectric layer such that the firstinterdigital transducer electrode is positioned closer to the cavitythan to the first solid acoustic mirror.

In one embodiment, the first solid acoustic mirror includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers of first solid acoustic mirror.The second solid acoustic mirror can include alternating low impedancelayers and high impedance layers that has a higher impedance than thelow impedance layers of second solid acoustic mirror. The low impedancelayers of the first solid acoustic mirror and the low impedance layersof the second solid acoustic mirror can have different thicknesses.

In one embodiment, the first piezoelectric layer and the secondpiezoelectric layer are positioned between the first and secondsubstrates.

In one embodiment, the second substrate is disposed between the firstand second piezoelectric layers.

In one embodiment, at least one of the first acoustic wave device or thesecond acoustic wave device is a laterally excited bulk acoustic waveresonator.

In one embodiment, at least one of the first acoustic wave device or thesecond acoustic wave device is a leaky longitudinal surface acousticwave resonator.

In one embodiment, the first acoustic wave device has a single mirrorstructure and the second acoustic wave device has a double mirrorstructure.

In one aspect, an acoustic wave device assembly is disclosed. Theacoustic wave device assembly can include a first acoustic wave deviceand a second acoustic wave device. The first acoustic wave deviceincludes a first substrate, a first piezoelectric layer having a firstportion and a second portion, a first solid acoustic mirror disposedbetween the first substrate and the first piezoelectric layer, and afirst interdigital transducer electrode on the first portion of thefirst piezoelectric layer and covered by the second portion of the firstpiezoelectric layer. The second acoustic wave device includes a secondsubstrate, a second piezoelectric layer, a second solid acoustic mirrordisposed between the second substrate and the second piezoelectriclayer, and a second interdigital transducer electrode in contact withthe second piezoelectric layer. The second acoustic wave device isstacked over the first acoustic wave device. The first acoustic wavedevice and the second acoustic wave device are spaced by a spacerassembly such that a cavity is formed between the first acoustic wavedevice and the second acoustic wave device.

In one embodiment, the second interdigital transducer is embedded in thesecond piezoelectric layer.

In one embodiment, a thickness of the first portion of the firstpiezoelectric layer is greater than a thickness of the second portion ofthe second piezoelectric layer.

In one embodiment, the first solid acoustic mirror includes alternatinglow impedance layers and high impedance layers that has a higherimpedance than the low impedance layers of first solid acoustic mirror.The second solid acoustic mirror can include alternating low impedancelayers and high impedance layers that has a higher impedance than thelow impedance layers of second solid acoustic mirror. The low impedancelayers of the first solid acoustic mirror and the low impedance layersof the second solid acoustic mirror can have different thicknesses.

In one embodiment, the first piezoelectric layer and the secondpiezoelectric layer are positioned between the first and secondsubstrates.

In one embodiment, the second substrate is disposed between the firstand second piezoelectric layers.

In one embodiment, the first acoustic wave device has a single mirrorstructure and the second acoustic wave device has a double mirrorstructure.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

The present disclosure relates to U.S. patent application Ser. No.______ [Attorney Docket SKYWRKS.1269A1], titled “STACKED ACOUSTIC WAVEDEVICE ASSEMBLY,” filed on even date herewith, U.S. patent applicationSer. No. ______ [Attorney Docket SKYWRKS.1269A2], titled “STACKEDACOUSTIC WAVE DEVICES WITH SOLID ACOUSTIC MIRROR THEREBETWEEN,” filed oneven date herewith, U.S. patent application Ser. No. ______ [AttorneyDocket SKYWRKS.1269A3], titled “ASSEMBLY WITH PARTIALLY EMBEDDEDINTERDIGITAL TRANSDUCER ELECTRODE,” filed on even date herewith, andU.S. patent application Ser. No. ______ [Attorney DocketSKYWRKS.1269A4], titled “STACKED SINGLE MIRROR ACOUSTIC WAVE DEVICE ANDDOUBLE MIRROR ACOUSTIC WAVE DEVICE,” filed on even date herewith, theentire disclosure of which are hereby incorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1A is a schematic cross sectional side view of a laterally excitedbulk acoustic wave device.

FIG. 1B is a schematic top plan view of an interdigital transducer (IDT)electrode of the laterally excited bulk acoustic wave device of FIG. 1A.

FIGS. 2A-2B show schematic cross sectional side views showing heat flowin the laterally excited bulk acoustic wave device of FIG. 1A.

FIG. 3 is a schematic cross sectional side view of a baseline laterallyexcited bulk acoustic wave device.

FIG. 4A is graph of admittance of the baseline laterally excited bulkacoustic wave device of FIG. 3 .

FIG. 4B illustrates displacement at a resonant frequency for thebaseline laterally excited bulk acoustic wave device of FIG. 3 .

FIG. 4C illustrates displacement at an anti-resonant frequency for thebaseline laterally excited bulk acoustic wave device of FIG. 3 .

FIG. 5 is a schematic cross sectional side view of a laterally excitedbulk acoustic wave device with a support substrate in contact with apiezoelectric layer.

FIG. 6A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 5 .

FIG. 6B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 5 .

FIG. 6C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 5 .

FIG. 7 is a schematic cross sectional side view of a laterally excitedbulk acoustic wave device with a solid acoustic mirror before designrefinement.

FIG. 8A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 7 .

FIG. 8B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 7 .

FIG. 8C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 7 .

FIG. 9 is a schematic cross sectional side view of a laterally excitedbulk acoustic wave device with a solid acoustic mirror.

FIG. 10A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 9 .

FIG. 10B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 .

FIG. 10C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 .

FIG. 10D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave deviceof FIG. 9 .

FIG. 10E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device of FIG. 9 .

FIG. 10F is a schematic cross sectional side view of a laterally excitedbulk acoustic wave device with a solid acoustic mirror and silicondioxide between interdigital transducer electrode fingers.

FIG. 10G is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device of FIG. 10F.

FIGS. 11A-13I are schematic cross sectional side views of stackedacoustic wave device assemblies according to various embodiment.

FIG. 14 is a schematic diagram of a ladder filter that includes alaterally excited bulk acoustic wave resonator.

FIG. 15 is a schematic diagram of a lattice filter that includes alaterally excited bulk acoustic wave resonator.

FIG. 16 is a schematic diagram of a hybrid ladder lattice filter thatincludes a laterally excited bulk acoustic wave resonator.

FIG. 17A is a schematic diagram of an acoustic wave filter.

FIG. 17B is a schematic diagram of a duplexer.

FIG. 17C is a schematic diagram of a multiplexer with hard multiplexing.

FIG. 17D is a schematic diagram of a multiplexer with switchedmultiplexing.

FIG. 17E is a schematic diagram of a multiplexer with a combination ofhard multiplexing and switched multiplexing.

FIG. 18 is a schematic diagram of a radio frequency module that includesan acoustic wave filter.

FIG. 19 is a schematic block diagram of a module that includes anantenna switch and duplexers.

FIG. 20 is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers.

FIG. 21 is a schematic block diagram of a module that includes a lownoise amplifier, a radio frequency switch, and filters.

FIG. 22 is a schematic diagram of a radio frequency module that includesan acoustic wave filter.

FIG. 23 is a schematic block diagram of a wireless communication devicethat includes a filter.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Laterally excited bulk acoustic wave resonators can be included inacoustic wave filters for high frequency bands, such as frequency bandsabove 3 Gigahertz (GHz) and/or frequency bands above 5 GHz. Suchfrequency bands can include a fifth generation (5G) New Radio (NR)operating band. Certain laterally excited bulk acoustic wave resonatorscan include an interdigital transducer (IDT) electrode on a relativelythin piezoelectric layer. A bulk acoustic wave (BAW) mode excited by theIDT electrode is not strongly affected by the pitch of IDT electrode incertain applications. Accordingly, the BAW resonator can have a higheroperating frequency than certain conventional surface acoustic wave(SAW) resonators. Certain laterally excited bulk acoustic waveresonators can be free standing. However, heat dissipation can beundesirable for such free standing laterally excited bulk acoustic waveresonators. Power durability and/or mechanical ruggedness of suchlaterally excited bulk acoustic wave resonators can be a technicalconcern. Free standing laterally excited bulk acoustic wave resonatorswith lithium niobate or lithium tantalate piezoelectric layers canencounter problems related to power durability in, for example, transmitfilter applications.

Heat dissipation and mechanical ruggedness can be improved by bonding apiezoelectric layer to a support substrate with a relatively highthermal conductivity. By bonding the piezoelectric layer directly to thesupport substrate, resonant characteristics can be degraded by leakageinto support substrate.

Aspects of this disclosure relate to a laterally excited bulk acousticwave resonator with a solid acoustic mirror positioned between apiezoelectric layer and a support substrate, and a stacked structureincluding the laterally excited bulk acoustic wave resonator. An IDTelectrode can be positioned on the piezoelectric layer. The supportsubstrate can have a relatively high thermal conductivity. For example,the support substrate can be a silicon support substrate. The solidacoustic mirror, which can be an acoustic Bragg reflector, can reduceand/or eliminate leakage into the support substrate. With such astructure, acoustic energy can be confined over the solid acousticmirror effectively and heat can flow though the support substrate withthe relatively high thermal conductivity. Mechanical ruggedness of sucha laterally exited bulk acoustic wave resonator can be improved byavoiding an air cavity between the piezoelectric layer and the supportsubstrate. At the same time, a relatively high frequency resonance canbe achieved with desirable power durability.

A laterally excited bulk acoustic wave device including any suitablecombination of features disclosed herein can be included in a filterarranged to filter a radio frequency signal in a fifth generation 5G NRoperating band within Frequency Range 1 (FR1). A filter arranged tofilter a radio frequency signal in a 5G NR operating band can includeone or more laterally excited bulk acoustic wave device disclosedherein. FR1 can be from 410 MHz to 7.125 GHz, for example, as specifiedin a current 5G NR specification.

A laterally excited bulk acoustic wave device disclosed herein can beincluded in a filter arranged to filter a radio frequency signal havinga frequency above FR1. For example, a laterally excited bulk acousticwave device can be included in a filter arranged to filter radiofrequency signals in a range from 10 GHz to 25 GHz. In applicationswhere such high frequency signals are being transmitted, higher transmitpowers can be used to account for higher loss in communication channelsat higher frequencies. Accordingly, thermal dissipation at highfrequencies of laterally excited bulk acoustic wave devices disclosedherein can be desirable.

In certain 5G applications, the thermal dissipation of the acoustic wavedisclosed herein can be advantageous. For example, such thermaldissipation can be desirable in 5G applications with a highertime-division duplexing (TDD) duty cycle compared to fourth generation(4G) Long Term Evolution (LTE) applications. As another example, therecan be more ganging of filters and carrier aggregation in 5Gapplications than 4G LTE applications. Accordingly, signals can havehigher power to account for losses associated with such ganging offilters and/or carrier aggregation. Thermal dissipation of laterallyexcited bulk acoustic wave devices disclosed can be implemented in theseexample applications to improve performance of filters.

Another type of acoustic wave resonators that can be used for frequencybands above 3 Gigahertz (GHz) and/or frequency bands above 5 GHz is theleaky longitudinal surface acoustic wave resonator, or LLSAW resonator.Leaky longitudinal surface acoustic wave resonators provide smallpropagation losses and high velocities. Suitable materials includelithium niobate and lithium tantalate. For example, for thepiezoelectric layer of a leaky longitudinal surface acoustic wavedevice, a lithium niobate crystal may be cut along a plane with Eulerangles of (α, β, γ), with α between 80° and 100°, β between 80° and100°, and γ between 30° and 50°. Especially preferred is a lithiumniobate crystal cut along a plane with Euler angles of (α, β, γ)=(90°,90°, 40°). Alternatively, for the piezoelectric layer of a leakylongitudinal surface acoustic wave device, a lithium niobate crystal maybe cut along a plane with Euler angles of (α, β, γ), with α between −10°and +10°, β between 70° and 110°, and γ between 80° and 100°. Especiallypreferred is a lithium niobate crystal cut along a plane with Eulerangles of (α, β, γ)=(0°, 90°, 90°). Aspects of this disclosure thus alsorelate to a leaky longitudinal surface acoustic resonator with a solidacoustic mirror positioned between a piezoelectric layer and a supportsubstrate. All features and variants that are described herein withrespect to laterally excited bulk acoustic wave resonators may also beapplied (if necessary, mutatis mutandis) to leaky longitudinal surfaceacoustic wave resonators. Most embodiments and variants herein will bedescribed with respect to laterally excited bulk acoustic waveresonators, laterally excited bulk acoustic wave devices, laterallyexcited bulk acoustic wave filters and so on. It shall be understoodthat, unless explicitly mentioned, the same embodiments and variants mayalso be provided with leaky longitudinal surface acoustic waveresonators, leaky longitudinal surface acoustic wave devices, leakylongitudinal surface acoustic wave filters and so on instead or inaddition.

One or more laterally excited bulk acoustic wave devices and/or one ormore leaky longitudinal surface acoustic wave devices in accordance withany suitable principles and advantages disclosed herein can be includedin a filter (i.e. an acoustic wave filter) arranged to filter a radiofrequency signal in a 4G LTE operating band and/or in a filter having apassband that includes a 4G LTE operating band and a 5G NR operatingband.

FIG. 1A is a cross sectional diagram of a laterally excited bulkacoustic wave device 28 with a solid acoustic mirror 15 according to anembodiment. The laterally excited bulk acoustic wave device 28 can be alaterally excited bulk acoustic wave resonator included in a filter. Thelaterally excited bulk acoustic wave device 28 can be any other suitablelaterally excited bulk acoustic wave device, such as a device in a delayline. The laterally excited bulk acoustic wave device 28 can beimplemented in relatively high frequency acoustic wave filters. Suchacoustic wave filters can filter radio frequency signals havingfrequencies above 3 GHz and/over above 5 GHz. The laterally excited bulkacoustic wave device 28 can be any other suitable laterally excited bulkacoustic wave device, such as a device in a delay line. As illustrated,the laterally excited bulk acoustic wave device 28 includes a supportsubstrate 17, a solid acoustic mirror 15 on the support substrate 17, apiezoelectric layer 12 on the solid acoustic mirror 15, and an IDTelectrode 14 on the piezoelectric layer 12. The IDT electrode 14 isarranged to laterally excite a bulk acoustic wave. The substrate 17 canfunction like a heat sink. The substrate 17 can provide thermaldissipation and improve power durability of the laterally excited bulkacoustic wave device 28.

The piezoelectric layer 12 can be a lithium based piezoelectric layer.For example, the piezoelectric layer 12 can be a lithium niobate layer.As another example, the piezoelectric layer 12 can be a lithiumtantalate layer. In certain applications, the piezoelectric layer 12 canbe an aluminum nitride layer. The piezoelectric layer 12 can be anyother suitable piezoelectric layer.

In certain surface acoustic wave resonators, there can be horizontalacoustic wave propagation. In such surface acoustic wave resonators, IDTelectrode pitch can set the resonant frequency. Limitations ofphotolithography can set a lower bound on IDT electrode pitch and,consequently, resonant frequency of certain surface acoustic waveresonators.

The laterally excited bulk acoustic wave device 28 can generate a Lambwave that is laterally excited. A resonant frequency of the laterallyexcited bulk acoustic wave device 28 can depend on a thickness H1 of thepiezoelectric layer 12. The thickness H1 of the piezoelectric layer 12can be a dominant factor in determining the resonant frequency for thelaterally excited bulk acoustic wave device 28. The pitch of the IDTelectrode 14 can be a second order factor in determining resonantfrequency of the laterally excited bulk acoustic wave device 28. Athickness of a low impedance layer, such as a silicon dioxide layer,directly under the piezoelectric layer 12 can have a secondary impact onthe resonant frequency of the laterally excited bulk acoustic wavedevice 28. The thickness of such a low impedance layer can be sufficientto adjust resonant frequency for a shunt resonator and a seriesresonator of a filter.

A combination of the thickness H1 of the piezoelectric layer 12 andacoustic velocity in the piezoelectric layer 12 can determine theapproximate resonant frequency of the laterally excited bulk acousticwave device 28. The resonant frequency can be increased by making thepiezoelectric layer 12 thinner and/or by using a piezoelectric layer 12with a higher acoustic velocity.

The piezoelectric layer 12 can be manufactured with a thickness H1 thatis 0.2 micrometers or higher from the fabrication point of view. Thepiezoelectric layer 12 can have a thickness in a range from 0.2micrometers to 0.4 micrometers in certain applications. Thepiezoelectric layer can have a thickness in a range from 0.2 micrometersto 0.3 micrometers. In certain applications, the piezoelectric layer canhave a thickness H1>0.04L from the electrical performance (K2) point ofview, in which L is IDT electrode pitch.

The laterally excited bulk acoustic wave device 28 with a 0.2 micrometerthick aluminum nitride piezoelectric layer 12 can have a resonantfrequency of approximately 25 GHz. The laterally excited bulk acousticwave device 28 with a 0.2 micrometer thick lithium niobate piezoelectriclayer 12 can have a resonant frequency of approximately 10 GHz. Thelaterally excited bulk acoustic wave device 28 with a 0.4 micrometerthick lithium niobate piezoelectric layer 12 can have a resonantfrequency of approximately 5 GHz. Based on the piezoelectric materialsand thickness of the piezoelectric layer, the resonant frequency of thelaterally excited bulk acoustic wave device 28 can be designed forfiltering an RF signal having a particular frequency.

Odd harmonics for a laterally excited bulk acoustic wave resonator canhave a k2 that is sufficiently large for a ladder filter in certainapplications. Such odd harmonics (e.g., a 3rd harmonic) can have a k2that is proportional to fundamental mode k2. A laterally excited bulkacoustic wave resonator using an odd harmonic can have a lithium niobatepiezoelectric layer. The electromechanical coupling factor k2 (or, moreformally, k²), is usually defined by, where fs and fp are thefrequencies of the resonance and anti-resonance respectively:

${k^{2} = {\frac{\pi}{2}\frac{f_{s}}{f_{p}}{\tan\left( {\frac{\pi}{2}\frac{\Delta f}{f_{p}}} \right)}}};{and}$Δf = fs − fp.

Filters that include one or more laterally excited bulk acoustic wavedevices 28 can filter radio frequency signals up to about 10 GHz with arelatively wide bandwidth. Filters that include one or more laterallyexcited bulk acoustic wave devices 28 can filter radio frequency signalshaving a frequency in a range from 10 GHz to 25 GHz. In some instances,a filter that include one or more laterally excited bulk acoustic wavedevices 28 can filter an RF signal having a frequency in a range from 3GHz to 5 GHz, a range from 4.5 GHz to 10 GHz, a range from 5 GHz to 10GHz, or a range from 10 GHz to 25 GHz.

In the laterally excited bulk acoustic wave device 28, the IDT electrode14 is over the piezoelectric layer 12. As illustrated, the IDT electrode14 has a first side in physical contact with the piezoelectric layer 12and a second side in physical contact with a layer of the solid acousticmirror 16. The IDT electrode 14 can include aluminum (Al), molybdenum(Mo), tungsten (W), gold (Au), silver (Ag), copper (Cu), platinum (Pt),ruthenium (Ru), titanium (Ti), the like, or any suitable combination oralloy thereof. The IDT electrode 14 can be a multi-layer IDT electrodein some applications.

The solid acoustic mirror 15 includes alternating low impedance layers20 (20A and 20B)and high impedance layers 22 (22A and 22B). Accordingly,the solid acoustic mirror 15 is an acoustic Bragg reflector. The lowimpedance layers 20 can be any suitable low impedance material such assilicon dioxide (SiO2) or the like. The high impedance layers 22 can beany suitable high impedance material such as platinum (Pt), tungsten(W), iridium (Ir), aluminum nitride (AlN), molybdenum (Mo), or the like.

As illustrated, the layer of the solid acoustic mirror 15 closest to thepiezoelectric layer 12 is a low impedance layer 20. Having a lowimpedance layer 20 closest to the piezoelectric layer 12 can increase anelectromechanical coupling coefficient (k2) of the laterally excitedbulk acoustic wave device 28 and/or bring a temperature coefficient offrequency (TCF) of the laterally excited bulk acoustic wave device 28closer to 0 in certain instances.

As illustrated, the layer of the solid acoustic mirror 15 closest to thesubstrate 17 is a high impedance layer 22. Having a high impedance layer22 closest to the substrate 17 can increase reflection of the layer ofthe solid acoustic mirror 15 closest to the substrate 17. Alternatively,a solid acoustic mirror (not illustrated) with a low impedance layer 20closest to the substrate 17 can have a higher adhesion with thesubstrate 17. For example, when the substrate 17 is a silicon substrate,the substrate should have a higher adhesion with a solid acoustic mirrorwith a silicon dioxide low impedance layer 20 that is closest to thesupport substrate (not illustrated) relative to the having a platinumhigh impedance layer 22 closest to the substrate 17. A low impedancelayer of an acoustic mirror in contact with the substrate 17 can have areduced thickness compared to other low impedance layers of the acousticmirror in certain applications.

The solid acoustic mirror 15 can confine acoustic energy. The solidacoustic mirror 15 can confine acoustic energy such that the supportsubstrate 17 is free from acoustic energy during operation of thelaterally excited bulk acoustic wave device 28. At least one of the lowimpedance layers 20 and/or at least one of the high impedance layers 22can be free from acoustic energy during operation of the laterallyexcited bulk acoustic wave device 28.

The support substrate 17 can dissipate heat associated with generating alaterally excited bulk acoustic wave. The support substrate 17 can beany suitable support substrate. The support substrate 17 can have arelatively high thermal conductivity to dissipate heat associated withoperation of the laterally excited bulk acoustic wave device 28. Thesupport substrate 17 can be a silicon substrate. The support substrate17 being a silicon substrate can be advantageous for processing duringmanufacture of the laterally excited bulk acoustic wave device 28 andprovide desirable thermal conductivity. Silicon is also a relativelyinexpensive material. The support substrate 17 can be an aluminumnitride substrate. In some other applications, the support substrate 17can be a quartz substrate, a ceramic substrate, a glass substrate, aspinel substrate, a magnesium oxide spinel substrate, a sapphiresubstrate, a diamond substrate, a diamond like carbon substrate, asilicon carbide substrate, a silicon nitride substrate, or the like.

FIG. 1B illustrates the IDT electrode 14 of the laterally excited bulkacoustic wave device 28 of FIG. 1A in plan view. Only the IDT electrode14 of the laterally excited bulk acoustic wave device 28 is shown inFIG. 1B. The IDT electrode 14 includes a bus bar 24 and IDT fingers 26extending from the bus bar 24. The IDT fingers 26 have a pitch of λ. Asdiscussed above, the pitch λ can have less impact than the thickness ofthe piezoelectric layer 12 in the laterally excited bulk acoustic wavedevice 28. The laterally excited bulk acoustic wave device 28 caninclude any suitable number of IDT fingers 26.

FIGS. 2A-2B show cross sectional views showing heat flow in thelaterally excited bulk acoustic wave device 28 of FIG. 1A. Duringoperation, heat can be generated by the IDT electrode 14. This heat canflow through the piezoelectric layer 12 and the solid acoustic mirror 15to the substrate 17. Accordingly, the solid acoustic mirror 15 canprovide a heat flow path from the piezoelectric layer 12 to thesubstrate 17. The substrate 17 can have a relatively high thermalconductivity and provide heat dissipation. The substrate 17 can increasemechanical durability.

FIG. 3 is a cross sectional diagram of a baseline laterally excited bulkacoustic wave device 30. As illustrated, the baseline laterally excitedbulk acoustic wave device 30 includes a piezoelectric layer 12 and anIDT electrode 14 on the piezoelectric layer 12. The laterally excitedbulk acoustic wave device 30 can be a free standing device supportedover a support substrate. There can be an air cavity positioned betweenthe piezoelectric layer 12 and the support substrate.

FIG. 4A is graph of admittance of the baseline laterally excited bulkacoustic wave device 30 of FIG. 3 . This graph shows a relatively cleanfrequency response with a resonant frequency at around 4.8 GHz and ananti-resonant frequency around 5.4 GHz.

FIG. 4B illustrates displacement at a resonant frequency for thebaseline laterally excited bulk acoustic wave device 30 of FIG. 3 . FIG.4B indicates displacement in the piezoelectric layer 12 at the resonantfrequency.

FIG. 4C illustrates displacement at an anti-resonant frequency for thebaseline laterally excited bulk acoustic wave device 30 of FIG. 3 . FIG.4C indicates displacement in the piezoelectric layer 12 at theanti-resonant frequency.

FIG. 5 is a cross sectional diagram of a laterally excited bulk acousticwave device 50 with a support substrate in contact with a piezoelectriclayer. As illustrated, the laterally excited bulk acoustic wave device50 includes a piezoelectric layer 12, an IDT electrode 14 on a firstside of the piezoelectric layer 12, and a support substrate 17 incontact with a second side of the piezoelectric layer 12 that isopposite to the first side. The support substrate 17 can be a siliconsubstrate. The support substrate 17 can dissipate heat associated withoperation of the laterally excited bulk acoustic wave device 50.

FIG. 6A is graph of admittance of the laterally excited bulk acousticwave device 50 of FIG. 5 , in which the support substrate 17 is asilicon substrate. This graph indicates that the laterally excited bulkacoustic wave device 50 produces a low quality factor (Q) that isgenerally undesirable for an acoustic wave filter.

FIG. 6B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device 50 of FIG. 5 , in which thesupport substrate 17 is a silicon substrate. FIG. 6B indicates acousticenergy leakage into the silicon substrate at the resonant frequency.

FIG. 6C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device 50 of FIG. 5 , in which thesupport substrate 17 is a silicon substrate. FIG. 6B indicates acousticenergy leakage into the silicon substrate at the anti-resonantfrequency.

FIG. 7 is a cross sectional diagram of a laterally excited bulk acousticwave device 70 with a solid acoustic mirror according to an embodimentbefore design refinement and/or optimization. The laterally excited bulkacoustic wave device 70 includes a piezoelectric layer 12, aninterdigital transducer electrode 14 on the piezoelectric layer 12, asolid acoustic mirror 15 including alternating low impedance layers 20and high impedance layers 22, and a support substrate 17. The solidacoustic mirror 15 is positioned between the support substrate 17 andthe piezoelectric layer 12. The solid acoustic mirror 15 is notoptimized in the laterally excited bulk acoustic wave device 70. In FIG.7 , the support substrate 17 is not necessarily shown to scale. Thesupport substrate 17 can be the thickest element illustrated in thelaterally excited bulk acoustic wave device 70.

In the simulations for FIGS. 8A to 8C, the acoustic mirror includessilicon dioxide low impedance layers having a thickness of 0.1 λ andplatinum (Pt) high impedance layers having a thickness of 0.1 λ. Theperformance of the laterally excited bulk acoustic wave device 70 inthese simulations is degraded. This can be due to the high impedancelayers having a thickness that is away from range that leads to betterperformance.

FIG. 8A is graph of admittance of the laterally excited bulk acousticwave device 70 of FIG. 7 . This graph shows a generally undesirablefrequency response.

FIG. 8B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device 70 of FIG. 7 . FIG. 8Bindicates some acoustic energy leakage into the middle layers of thesolid acoustic mirror 15 at the resonant frequency.

FIG. 8C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device 70 of FIG. 7 . FIG. 8Cindicates acoustic energy leakage into the middle and lower layers ofthe solid acoustic mirror 15 at the anti-resonant frequency.

FIG. 9 is a cross sectional diagram of a laterally excited bulk acousticwave device 90 with a solid acoustic mirror according to an embodiment.The laterally excited bulk acoustic wave device 90 is like the laterallyexcited bulk acoustic wave device 70 of FIG. 7 , except that thelaterally excited bulk acoustic wave device 90 is modified to increaseconfinement of acoustic energy and produce a cleaner frequency response.In FIG. 9 , the support substrate 17 is not necessarily shown to scale.The support substrate 17 can be the thickest element illustrated in thelaterally excited bulk acoustic wave device 90.

The piezoelectric layer 12 can have a thickness to increase performanceof the laterally excited bulk acoustic wave device 90. For example, thepiezoelectric layer 12 can have a thickness in a range from about 0.04λto 0.5λ, in which λ is IDT electrode pitch. As one example, thepiezoelectric layer 12 can have a thickness of about 0.08λ.

The layers of the solid acoustic mirror 15 can each have a thickness toincrease performance of the laterally excited bulk acoustic wave device90. For example, the low impedance layers 20 can be silicon dioxidelayers having a thickness in a range from 0.02 λ to 0.10 λ. The highimpedance layers can be platinum layers having a thickness in a rangefrom 0.01 λ to 0.03 λ or 0.04 λ to 0.06 λ. As one example, the lowimpedance layers 20 and high impedance layers 22 can each have athickness of about 0.05λ. Preferred mirror layer thickness can vary formaterial. For example, in the case with high impedance layers that aretungsten, preferred thickness of the high impedance layer can be in arange from 0.017 λ to 0.027 λ or from 0.049 λ to 0.059 λ. For molybdenumhigh impedance layers, preferred thickness of each high impedance layercan be in a range from 0.040 λ to 0.050 λ or 0.010 λ to 0.011 λ.Normalized by wave length of longitudinal wave velocity λ_(p) in eachmaterial, preferred low impedance layer thickness for each silicondioxide low impedance layer can be in a range from 0.1 λ_(p) to 0.3λ_(p) and each high impedance layer thickness can be in a range from0.14 λ_(p) to from 0.30 λ_(p) or 0.35 λ_(p) to 0.45 λ_(p). In certainapplications, the low impedance layers 20 and the high impedance layers22 can have similar and/or approximately the same thicknesses. In someother applications, the low impedance layers 20 can have differentthickness than the high impedance layers 22.

FIG. 9 may also be used as a cross sectional diagram of a leakylongitudinal surface acoustic wave device. In such an acoustic wavedevice, the piezoelectric layer 12 may be formed, compared to thepiezoelectric layer 12 of the laterally excited bulk acoustic wavedevice 90, from a different material and/or may result from a differentcutting angle (or: cutting plane) through a crystal. For example, inorder to obtain a piezoelectric layer 12 for a laterally excited bulkacoustic wave device 90, a lithium niobate crystal may be cut along aplane with Euler angles of (α, β, γ), with α between −10° and 10°, βbetween −10° and 10°, and γ between 80° and 100°. Especially preferredis a lithium niobate crystal cut along a plane with Euler angles of (α,β, γ)=(0°, 0°, 90°).

By contrast, in order to obtain a piezoelectric layer 12 for a leakylongitudinal surface acoustic wave device, a lithium niobate crystal maybe cut along a plane with Euler angles of (α, β, γ), with α between 80°and 100°, β between 80° and 110°, and γ between 30° and 50°. Especiallypreferred is a lithium niobate crystal cut along a plane with Eulerangles of (α, β, γ)=(90°, 90°, 40°). Alternatively, in order to obtain apiezoelectric layer 12 for a leaky longitudinal surface acoustic wavedevice, a lithium niobate crystal may be cut along a plane with Eulerangles of (α, β, γ), with α between −10° and +10°, β between 70° and110°, and γ between 80° and 100°. Especially preferred is a lithiumniobate crystal cut along a plane with Euler angles of (α, β, γ)=(0°,90°, 90°). It shall be understood that in each case the solid acousticmirror 15 is designed and formed specifically for the type and frequencyrange of waves that each acoustic wave device utilizes.

The simulations in FIGS. 10A to 10C correspond to a piezoelectric layerthickness of 0.08 k and low impedance and high impedance layers 20 and22, respectively, each having a thickness of 0.05 k.

FIG. 10A is graph of admittance of the laterally excited bulk acousticwave device of FIG. 9 . This graph shows a relatively clean frequencyresponse with a resonant frequency at around 4.6 GHz and ananti-resonant frequency around 5.0 GHz

FIG. 10B illustrates displacement at a resonant frequency for thelaterally excited bulk acoustic wave device FIG. 9 . FIG. 10B indicatesthat the acoustic energy in confined near the piezoelectric layer 12 atthe resonant frequency in the laterally excited bulk acoustic wavedevice 90. FIG. 10B shows improve acoustic energy confinement relativeto FIG. 8B.

FIG. 10C illustrates displacement at an anti-resonant frequency for thelaterally excited bulk acoustic wave device of FIG. 9 . FIG. 10Cindicates that the acoustic energy in confined near the piezoelectriclayer 12 at the anti-resonant frequency in the laterally excited bulkacoustic wave device 90. FIG. 10C shows improve acoustic energyconfinement relative to FIG. 8C.

FIG. 10D is a graph corresponding to different thicknesses of thepiezoelectric layer for the laterally excited bulk acoustic wave device90 of FIG. 9 . The different curves correspond to different thicknessesH1 for a lithium niobate piezoelectric layer 12. FIG. 10D indicates thatthe thickness H1 of the lithium niobate piezoelectric layer 12 can be atleast 0.06 L to achieve a preferred electrical performance (k2). Thethickness H1 of lithium niobate piezoelectric layer 12 can be at least300 nanometers from a fabrication point of view.

FIG. 10E is a graph corresponding to different thicknesses of theinterdigital transducer electrode for the laterally excited bulkacoustic wave device 90 of FIG. 9 . The different curves correspond todifferent thicknesses H2 for the IDT electrode layer 14. This graphindicates that an IDT electrode thickness H2 of greater than 0.02 L canexcite a spurious mode. The simulations in FIG. 10E do not include theeffect of IDT electrode resistivity.

FIG. 10F is a cross sectional diagram of a laterally excited bulkacoustic wave device 100 with a solid acoustic mirror 15 and silicondioxide 102 between fingers of the IDT electrode 14 according to anembodiment. The laterally excited bulk acoustic wave device 100 is likethe laterally excited bulk acoustic wave device 90 of FIG. 9 , exceptthat silicon dioxide 102 is included between fingers of the IDTelectrode 14. In some other instances (not illustrated), silicon dioxideand/or another temperature compensation layer can cover fingers of theIDT electrode 14.

Including silicon dioxide 102 between fingers of the IDT electrode 102can suppress a spurious mode by thicker IDT electrodes. Resonantfrequency can be dominated by total thickness of the piezoelectric layer12 and silicon dioxide 102. An upper silicon dioxide layer 102 canprovide frequency tuning. A trimming range can be sufficient to coverseries and parallel arms in a ladder type filter.

FIG. 10G is a graph corresponding to different thicknesses of the IDTelectrode 14 for the laterally excited bulk acoustic wave device 100 ofFIG. 10F. The simulations in FIG. 10G do not include the effect of IDTelectrode resistivity.

FIG. 11A is a schematic cross sectional side view of a stacked acousticwave device assembly 200 a according to an embodiment, not necessarilyshown to scale. The stacked acoustic wave device assembly 200 a has arelatively small footprint while at the same time including both a firstacoustic wave device 210 and a second acoustic wave device 220. Thefirst acoustic wave device 210 includes a first support substrate 217and a first piezoelectric layer 212. For example, the first supportsubstrate 217 and the first piezoelectric layer 212 may be formed withthe same properties as the support substrate 17 and the piezoelectriclayer 12, respectively, described herein with respect to FIG. 9 . Thefirst acoustic wave device 210 can include a first solid acoustic mirror215 that is positioned between the first support substrate 217 and thefirst piezoelectric layer 212. For example, between the first supportsubstrate 217 and the first piezoelectric layer 212, the first solidacoustic mirror 215 can be positioned. The first acoustic mirror 215 canhave the same or generally similar structure as the solid acousticmirror 15 described herein. For example, as described herein, inparticular with respect to FIG. 9 and the solid acoustic mirror 15, thefirst solid acoustic mirror 215 may be formed with alternating lowimpedance layers 20 and high impedance layers 22, wherein a lowimpedance layer 20 is formed immediately adjacent to and in contact withthe first piezoelectric layer 212, and a high impedance layer 22 isformed immediately adjacent to and in contact with the first supportsubstrate 217 such that low impedance layers 20 and high impedancelayers 22 are provided in the same quantity. The number of pairs ofadjacent low impedance layers 20 and high impedance layers 22 may bebetween two and ten, between three and six, or even smaller or larger.

The second acoustic wave device 220 includes a second support substrate227 and a second piezoelectric layer 222. For example, the secondsupport substrate 227 and the second piezoelectric layer 222 may beformed with the same properties as the support substrate 17 and thepiezoelectric layer 12, respectively, described herein with respect toFIG. 9. The second acoustic wave device 220 can include a second solidacoustic mirror 225 that is positioned between the second supportsubstrate 227 and the second piezoelectric layer 222. For example,between the second support substrate 227 and the second piezoelectriclayer 222, a second solid acoustic mirror 225 can be positioned. Thesecond solid acoustic mirror 225 can have the same or generally similarstructure as the solid acoustic mirror 15 described herein. For example,as described herein, in particular with respect to FIG. 9 and the solidacoustic mirror 15, the second solid acoustic mirror 225 may be formedwith alternating low impedance layers 20 and high impedance layers 22. Alow impedance layer 20 may be formed immediately adjacent to and incontact with the second piezoelectric layer 222, and a high impedancelayer 22 may be formed immediately adjacent to and in contact with thesecond support substrate 227 such that low impedance layers 20 and highimpedance layers 22 are provided in the same quantity. The number ofpairs of adjacent low impedance layers 20 and high impedance layers 22may be between two and ten, between three and six, or even smaller orlarger. The first solid acoustic mirror 215 and the second solidacoustic mirror 225 may be identical or different from one another. Insome variants, the first acoustic wave device 210 and the secondacoustic wave device 220 are provided identically, for example when thefirst acoustic wave device 210 realizes a first acoustic wave filter andthe second acoustic wave device 220 realizes a second acoustic wavefilter with the same frequency range as the first acoustic wave filter.

As is shown in FIG. 11A, the first acoustic wave device 210 and thesecond acoustic wave device 220 are stacked using a spacer assembly 201such that a cavity 202 is formed between the first acoustic wave device210 and the second acoustic wave device 220 and such that the firstpiezoelectric layer 212 and the second piezoelectric layer 222 face eachother across the cavity 202. The spacer assembly 201 may include, orconsist of, a plurality of columns 201 a, 201 b that are attached on oneof their longitudinal ends to the first piezoelectric layer 212 and onanother of their longitudinal ends to the second piezoelectric layer 222such that the cavity 202 is formed with particular dimensions. Theparticular dimensions of the cavity 202 can be pre-defined and/or fixeddimensions. The columns 201 a, 201 b of the spacer assembly 201 may, forinstance, be formed of a metal or metal alloy, for example of copper(Cu) or gold (Au). Forming the spacer assembly 201 from such metals withgood heat conductivity may help with heat management. In someapplications, the piezoelectric layers 212, 222 can produce heat when inuse (e.g., during operation of the stacked acoustic wave device assemblyin an acoustic wave filter). The spacer assembly 201 can help intransporting, transferring, or dissipating heat from one piezoelectriclayer 212, 222 to the respective other. In this way, each of thesubstrates 217, 227 may contribute to waste heat removal even when onlyone of the acoustic wave devices 210, 220 is currently producing theheat. Thus, the stacked acoustic wave device assembly 200 a not only hasa small footprint due to the stacking, but heat can be transported awayon two different levels, or from two different locations, e.g., at therespective support substrate 217, 227.

In the shown embodiment, a first IDT electrode 214 of the first acousticwave device 210 is formed on the first piezoelectric layer 212 such thatit protrudes entirely into the cavity 202, and a second IDT electrode224 of the second acoustic wave device 220 is formed on the secondpiezoelectric layer 222 such that it protrudes entirely into the cavity202. Both the first IDT electrode 214 and the second IDT electrode 224can be formed as has been described in the foregoing with respect to theIDT electrode 14, for example with respect to FIG. 9 . It shall beunderstood that the figures, including FIG. 11A, are not drawn to scale,in particular that distances between an area of the piezoelectric layers212, 222 where the IDT electrodes 214, 224 are formed and areas of thepiezoelectric layers 212, 222 where the columns 201 of the spacerassembly 201 are attached. It shall be understood that in acoustic wavedevices, usually two separate IDT electrodes are provided withconsiderable distance there between. The drawing in FIG. 11A is intendedto illustrate the vertical arrangement of the acoustic wave devices 210,220 and is not intended to depict or restrict the layout in thehorizontal direction.

The stacked acoustic wave device assembly 200 a can be produced byproducing a first wafer with one or more, usually a large number, ofacoustic wave devices horizontally adjacent to one another, producing asecond wafer with preferably the same number of acoustic wave deviceshorizontally adjacent to one another, then flipping one of the wafers,and bonding the wafers facing each other with a plurality of spacerassemblies 201, in particular columns 201 a, 201 b. Thereafter, theindividual stacked acoustic wave device assemblies 200 a can be providedby dicing the wafers bonded to one another. In a variant, the acousticwave devices can be produced on a wafer, the wafer can be cut in half,and then one half is used as the first wafer and the other half is usedas the second wafer in the above description.

Each of the first acoustic wave device 210 and the second acoustic wavedevice 220 may be realized as a laterally excited bulk acoustic wavedevice. Each of the first acoustic wave device 210 and the secondacoustic wave device 220 may also be realized as a leaky longitudinalsurface acoustic wave device. In other words, both of the first acousticwave device 210 and the second acoustic wave device 220 may be realizedas a laterally excited bulk acoustic wave device, or both of the firstacoustic wave device 210 and the second acoustic wave device 220 may berealized as a leaky longitudinal surface acoustic wave device, or onemay be realized as a laterally excited bulk acoustic wave device and theother one as a leaky longitudinal surface acoustic wave device. Bothlaterally excited bulk acoustic wave device and leaky longitudinalsurface acoustic wave device have been described with respect to FIG. 9herein.

In case one (or both) of the acoustic wave devices 210, 220 of thestacked acoustic wave device assembly 200 a is (or are) a laterallyexcited bulk acoustic wave device (such as laterally excited bulkacoustic wave device 90 of FIG. 9 ), specifics about materials (e.g.silicon dioxide, tungsten, molybdenum, . . . ), dimensions (e.g.thickness in a range from 0.01 λ to 0.5 λ) of any or all layers 20, 22,212, 222 and substrates 217, 227 and the like can be found in theforegoing discussion, specifically with respect to FIG. 9 .

In case one (or both) of the acoustic wave devices 210, 220 of thestacked acoustic wave device assembly 200 a is (or are) a leakylongitudinal surface acoustic wave device, the same materials,dimensions and so on may apply, with the difference that the respectivepiezoelectric layer 212, 222 is formed such as to transmit leakylongitudinal surface waves. For example, the respective piezoelectriclayer 212, 222 may be formed of a lithium niobate crystal cut along aplane with Euler angles (α, β, γ), with α between 80° and 100°, βbetween 80° and 110°, and γ between 30° and 50°. Especially preferred isa lithium niobate crystal cut along a plane with Euler angles of (α, β,γ)=(90, 90, 40°). Alternatively, the piezoelectric layer 212, 222 isformed of a lithium niobate crystal cut along a plane with Euler anglesof (α, β, γ), with α between −10° and +10°, β between 70° and 110°, andγ between 80°and 100°. Especially preferred is a lithium niobate crystalcut along a plane with Euler angles of (α, β, γ)=(0°, 90°, 90°).

FIG. 11B is a schematic cross sectional side view of a stacked acousticwave device assembly 200 b according to an embodiment, not necessarilyshown to scale. The stacked acoustic wave device assembly 200 b of FIG.11B can be seen as a variant of the stacked acoustic wave deviceassembly 200 a of FIG. 11A. A first acoustic wave device 230 of thestacked acoustic wave device assembly 200 b of FIG. 11B differs from thefirst acoustic wave device 210 of the stacked acoustic wave deviceassembly 200 a of FIG. 11A only in the differences between therespective first piezoelectric layers 212, 232 and in the differencesbetween the respective first IDT electrodes 214, 234. Specifically, inthe stacked acoustic wave device assembly 200 b of FIG. 11B, the firstIDT electrode 234 is partially embedded within the first piezoelectriclayer 232 such that one group of surfaces of the first IDT electrode 234is open to the cavity 202 and that the other surfaces of the first IDTelectrode 234 are covered by the first piezoelectric layer 232. Thesurfaces of the one group of surfaces of the first IDT electrode 234 liewithin the same plane and are arranged flush with a surface of the firstpiezoelectric layer 232 which faces the cavity 202. Expressed in yetanother way, the first acoustic wave device 230 faces the cavity 202with a flush planar surface which is formed in part by a surface of thefirst piezoelectric layer 232 and in part by the only open surfaces ofthe first IDT electrode 234.

Similarly, a second acoustic wave device 240 of the stacked acousticwave device assembly 200 b of FIG. 11B differs from the second acousticwave device 220 of the stacked acoustic wave device assembly 200 a ofFIG. 11A only in the differences between the respective secondpiezoelectric layers 222, 242 and in the differences between therespective second IDT electrodes 224, 244. Specifically, in the stackedacoustic wave device assembly 200 b of FIG. 11B, the second IDTelectrode 244 is partially embedded within the second piezoelectriclayer 242 such that one group of surfaces of the second IDT electrode244 is open to the cavity 202 and that the other surfaces of the secondIDT electrode 244 are covered by the second piezoelectric layer 242. Thesurfaces of the one group of surfaces of the second IDT electrode 244lie within the same plane and are arranged flush with a surface of thesecond piezoelectric layer 242 which faces the cavity 202. Expressed inyet another way, the second acoustic wave device 240 faces the cavity202 with a flush planar surface which is formed in part by a surface ofthe second piezoelectric layer 242 and in part by the only open surfacesof the second IDT electrode 244.

It shall be understood that, although it may be convenient in particularfor the manufacture to provide the stacked acoustic wave device assembly200 a as shown in FIG. 11A, the design shown for the acoustic wavedevices 230, 240 in FIG. 11B may be used for one of the two acousticwave devices, and the design shown for the acoustic wave devices 210,210 in FIG. 11A may be used for the other of the two acoustic wavedevices of one stacked acoustic wave device assembly 200 b. In otherwords, one acoustic wave device may have an IDT electrode 214, 224 thatis arranged on (top of) a surface of a respective piezoelectric layer212, 222, and the other acoustic wave device may have an IDT electrode234, 244 that is partially embedded within the surface of the respectivepiezoelectric layer 232, 242. Providing IDT electrodes on top ofpiezoelectric layers may simplify the manufacturing process. ProvidingIDT electrodes as partially embedded within the surface of piezoelectriclayers may improve k2, meaning an improved electrical performance, aswell as realize broader frequency bands.

FIG. 11C is a schematic cross sectional side view of a stacked acousticwave device assembly 200 c according to another embodiment, notnecessarily shown to scale. The stacked acoustic wave device assembly200 c of FIG. 11C can be seen as a variant of the stacked acoustic wavedevice assembly 200 a of FIG. 11A. A first acoustic wave device 250 ofthe stacked acoustic wave device assembly 200 c of FIG. 11C differs fromthe first acoustic wave device 210 of the stacked acoustic wave deviceassembly 200 a of FIG. 11A only in the differences between therespective first piezoelectric layers 212, 252 and in the differencesbetween the respective first IDT electrodes 214, 254. Specifically, inthe stacked acoustic wave device assembly 200 c of FIG. 11C, the firstIDT electrode 254 is completely embedded within the first piezoelectriclayer 232 such that all of the surfaces of the first IDT electrode 254are covered by the first piezoelectric layer 252. Providing IDTelectrodes as completely embedded within the surface of piezoelectriclayers may further improve k2, meaning an improved electricalperformance, as well as realize even broader frequency bands.

Similarly, a second acoustic wave device 260 of the stacked acousticwave device assembly 200 c of FIG. 11C differs from the second acousticwave device 220 of the stacked acoustic wave device assembly 200 a ofFIG. 11A only in the differences between the respective secondpiezoelectric layers 222, 262 and in the differences between therespective second IDT electrodes 224, 264. Specifically, in the stackedacoustic wave device assembly 200 c of FIG. 11C, the second IDTelectrode 264 is completely embedded within the second piezoelectriclayer 262 such all of the surfaces of the second IDT electrode 246 arecovered by the second piezoelectric layer 262. Providing IDT electrodesas completely embedded within the surface of piezoelectric layers mayfurther improve k2, meaning an improved electrical performance, as wellas realize even broader frequency bands.

Thus, referring to FIG. 11A, FIG. 11B and FIG. 11C , three differentarrangements of the IDT electrodes 214, 224, 234, 244, 254, 264 withrespect to their corresponding piezoelectric layer 212, 222, 232, 242,252, 262 have been described wherein the corresponding piezoelectriclayer 212, 222, 232, 242, 252, 262 is the one in which acoustic wavesare generated by the IDT electrodes 214, 224, 234, 244, 254, 264 in thecase of transmitting electrodes, or by which acoustic waves are receivedwhich induce a voltage in the case of receiving electrodes. The threedifferent arrangements are: (a) IDT electrode 214, 224 arranged on asurface of the piezoelectric layer 212, 222 facing the cavity 202; (b)IDT electrode 234, 244 arranged partially embedded into and flush withthe surface of the piezoelectric layer 232, 242; and (c) IDT electrode254, 264 arranged completely embedded within the piezoelectric layer252, 262 such that the IDT electrode 254, 264 is not open to the cavity202.

It shall be understood that in any particular embodiment of a stackedacoustic wave device assembly, the first acoustic wave device 210, 230,250 may include any of these three arrangements, and the second acousticwave device 220, 240, 260 may include any of these three arrangements.In FIG. 11A, FIG. 11B, and FIG. 11C in each case the case is shown inwhich both first and second acoustic wave devices 210, 220, 230, 240,250, 260 include the same arrangement of IDT electrode 214, 224, 234,244, 254, 264 with respect to piezoelectric layer 212, 222, 232, 242,252, 262. However, the skilled person will readily appreciate from theforegoing that the first and second acoustic wave devices 210, 220, 230,240, 250, 260 may include different arrangements of IDT electrode 214,224, 234, 244, 254, 264.

Similarly, two main modes, or types of piezoelectric layers 212, 222,232, 242, 252, 262 have been described in the foregoing: laterallyexcited bulk acoustic wave devices and leaky longitudinal surfaceacoustic wave devices. It will be appreciated by the skilled person thatany of these two types of piezoelectric layers 212, 222, 232, 242, 252,262 may be combined with any of the three types of arrangements of theof IDT electrode 214, 224, 234, 244, 254, 264 with respect topiezoelectric layer 212, 222, 232, 242, 252, 262, and this with any orboth of the two acoustic wave devices of a single stacked acoustic wavedevice assembly. Thus, at least six (two times three) differentvariations of the stacked acoustic wave device assembly are presentedfor each of the two acoustic wave devices, leading to thirty-sixdifferent variants in total. Of course the skilled person will alwaysconsider and provide the optimal configuration out of these thirty-sixvariants for any intended application. Since there are also otherpossible configurations, for example IDT electrodes partially embedded(e.g., half-submerged) in the surface of the piezoelectric layers (seeFIG. 11D), the actual number of variations at the disposal of theskilled person will be even higher. The freedom of design for stackedacoustic wave device assemblies 200 is thus vastly increased by thepresent disclosure, whereas, by virtue of the stacking of two acousticwave devices 210, 220, 230, 240, 250, 260 the footprint of the stackedacoustic wave device assembly 200 is extraordinarily small.

FIG. 11D is a schematic cross sectional side view of a stacked acousticwave device assembly 200 d according to an embodiment. Unless otherwisenoted components of the stacked acoustic wave device assembly 200 d canbe the same or similar to like components disclosed herein. The stackedacoustic wave device assembly 200 d is generally similar to the stackedacoustic wave device assembly 200 b shown in FIG. 11B. The stackedacoustic wave device assembly 200 d can include a first acoustic wavedevice 230′ and a second acoustic wave device 240′. The first acousticwave device 230′ can include a first IDT electrode 234′ that is at leastpartially embedded in a first piezoelectric layer 232′ and a second IDTelectrode 244′ that is at least partially embedded in a secondpiezoelectric layers 242′. A portion of the first IDT electrode 234′ canbe disposed over a surface of the first piezoelectric layer 232′ and ina cavity 202. A portion of the second IDT electrode 244′ can be disposedover a surface of the second piezoelectric layer 242′ and in a cavity202. An at least partially embedded IDT electrode, such as the first IDTelectrode 234′ and the second IDT electrode 244′, can beneficiallyconfine acoustic energy in the piezoelectric layer (e.g., the respectivefirst and second piezoelectric layers 232′, 242′).

FIG. 12A is a schematic cross sectional side view of an acoustic wavedevice assembly 200 e according to an embodiment. Unless otherwise notedcomponents of the acoustic wave device assembly 200 e can be the same orsimilar to like components disclosed herein. The acoustic wave deviceassembly 200 e can include a first acoustic wave device 210, a secondacoustic wave device 220, and a lid 270. The first acoustic wave device210 can include a first support substrate 217, a first piezoelectriclayer 212, a first solid acoustic mirror 215 that is positioned betweenthe first support substrate 217 and the first piezoelectric layer 212,and a first IDT electrode 214 over a surface of the first piezoelectriclayer 212. The second acoustic wave device 220 can include a secondsupport substrate 227, a second piezoelectric layer 222, a second solidacoustic mirror 225 that is positioned between the second supportsubstrate 217 and the second piezoelectric layer 212, and a second IDTelectrode 224 over a surface of the second piezoelectric layer 212.

The first acoustic wave device 210 and the second acoustic wave device220 can be stacked on one another. The first acoustic wave device 210and the second acoustic wave device 220 can be stacked on one anothersuch that the first IDT electrode 214 is positioned in a cavity 202 thatis defined at least partially by a spacer assembly 201, the firstpiezoelectric layer 212, and the second support substrate 227. The firstacoustic wave device 210 and the second acoustic wave device 220 can bestacked on one another such that the second IDT electrode 224 ispositioned in a cavity 202′ that is defined at least partially by aspacer assembly 201′, the second piezoelectric layer 222, and the lid270.

FIG. 12B is a schematic cross sectional side view of an acoustic wavedevice assembly 200 f according to an embodiment. Unless otherwise notedcomponents of the acoustic wave device assembly 200 f can be the same orsimilar to like components disclosed herein. The acoustic wave deviceassembly 200 e can include a first acoustic wave device 210, a secondacoustic wave device 220, and lids 270, 272. The first acoustic wavedevice 210 can include a first support substrate 217, a firstpiezoelectric layer 212, a first solid acoustic mirror 215 that ispositioned between the first support substrate 217 and the firstpiezoelectric layer 212, and a first IDT electrode 214 over a surface ofthe first piezoelectric layer 212. The second acoustic wave device 220can include a second support substrate 227, a second piezoelectric layer222, a second solid acoustic mirror 225 that is positioned between thesecond support substrate 217 and the second piezoelectric layer 212, anda second IDT electrode 224 over a surface of the second piezoelectriclayer 212.

The first acoustic wave device 210 and the second acoustic wave device220 can be stacked on one another. The first acoustic wave device 210and the second acoustic wave device 220 can be stacked on one anothersuch that the first support substrate 217, the first piezoelectric layer212, the first solid acoustic mirror 215, the second support substrate227, the second piezoelectric layer 222, the second solid acousticmirror 225 are positioned between the first IDT electrode 214 and thesecond IDT electrode 224. In some embodiments, the first supportsubstrate 217 and the second support substrate 227 can be portions ofthe same substrate. In some other embodiments, the first supportsubstrate 217 and the second support substrate 227 can share at least aportion of the same substrate, can include two separate substrates thatare coupled together. By sharing the same substrate, the total thicknessof the first support substrate 217 and the second support substrate 227of the acoustic wave device assembly 200 f can be smaller than the totalthickness of the first support substrate 217 and the second supportsubstrate 227 of, for example, FIGS. 11A-11D, and 12A. For example, thetotal thickness of the first support substrate 217 and the secondsupport substrate 227 of the acoustic wave device assembly 200 f can bebetween 30% and 70%, 40% and 70%, 30% and 60%, 40% and 60%, or 45% and55% of the total thickness of the first support substrate 217 and thesecond support substrate 227 of, for example, FIGS. 11A-11D, and 12A

FIG. 12C is a schematic cross sectional side view of an acoustic wavedevice assembly 200 g according to an embodiment. Unless otherwise notedcomponents of the acoustic wave device assembly 200 g can be the same orsimilar to like components disclosed herein. The acoustic wave deviceassembly 200 g can include a first acoustic wave device 210′, a secondacoustic wave device 220′, and lids 270, 272. The first acoustic wavedevice 210′ can include a first piezoelectric layer 212, a first solidacoustic mirror 215, and a first IDT electrode 214 over a surface of thefirst piezoelectric layer 212. The second acoustic wave device 220′ caninclude a second piezoelectric layer 222, a second solid acoustic mirror225, and a second IDT electrode 224 over a surface of the secondpiezoelectric layer 212. As shown in FIG. 12C, a support substrate (thefirst support substrate 217 and the second support substrate 227 shown,for example, in FIG. 12B) can be omitted. In some embodiments, the firstsolid acoustic mirror 215 can function as a support substrate for thesecond acoustic wave device 220′, and the second solid acoustic mirror225 can function as a support substrate for the first acoustic wavedevice 210′.

The first and second solid acoustic mirrors 215, 225 can together definean acoustic mirror structure. The first and second solid acousticmirrors 215, 225 can each include low impedance layers 20 and highimpedance layers 22. A thickness t1 of the low impedance layer 20 of thefirst solid acoustic mirror 215 can be the same or different from athickness t2 of the low impedance layer 20 of the second solid acousticmirror 225. A thickness t3 of the high impedance layer 22 of the firstsolid acoustic mirror 215 can be the same or different from a thicknesst4 of the low impedance layer 22 of the second solid acoustic mirror225. In some embodiments, when the thicknesses t1, t2, t3, t4 of the lowimpedance layers 20 and the high impedance layers 22 the same, the firstand second acoustic wave devices 210′, 220′ can share the same solidacoustic mirror.

The acoustic wave device assemblies 200 f, 200 g may provide arelatively thin overall thickness as compared to some other acousticwave device assemblies that includes two or more acoustic wave devicesthat are stacked on one another by reducing or omitting the thickness ofa support substrate. Thicknesses of the lids 270, 272 can be relativelythin. For example, the lids 270, 272 can have any thickness as long asthe lids 270, 272 provides sufficient protection for the IDT electrodes214, 224.

FIG. 12D is a schematic cross sectional side view of an acoustic wavedevice assembly 200 h according to an embodiment. Unless otherwise notedcomponents of the acoustic wave device assembly 200 h can be the same orsimilar to like components disclosed herein. The acoustic wave deviceassembly 200 h can include a first acoustic wave device 210, a secondacoustic wave device 274, and a spacer assembly 201 between the firstacoustic wave device 210 and the second acoustic wave device 274. Thefirst acoustic wave device 210 can include a first support substrate217, a first piezoelectric layer 212, a first solid acoustic mirror 215that is positioned between the first support substrate 217 and the firstpiezoelectric layer 212, and a first IDT electrode 214 over a surface ofthe first piezoelectric layer 212. The second acoustic wave device 274can include a second support substrate 227, a second piezoelectric layer222, a second solid acoustic mirror 225 that is positioned between thesecond support substrate 227 and the second piezoelectric layer 212, asecond IDT electrode 224 over a surface of the second piezoelectriclayer 212, a third support substrate 276, and a third solid acousticmirror 278. The first acoustic wave device 210 can have a single sidesolid acoustic mirror structure, and the second acoustic wave device 274can have a double side solid acoustic mirror structure.

Though in FIG. 12D, the first acoustic wave device 210 and the secondacoustic wave device 274 are stacked such that the spacer assembly 201is disposed between the first acoustic wave device 210 and the secondacoustic wave device 274 and the second support substrate 227 isdisposed between the second solid acoustic mirror 225 and the firstacoustic wave device 210, orientations of the first acoustic wave device210 and the second acoustic wave device 274 can be altered, in someembodiments. For example, the first acoustic wave device 210 can beflipped so as to position the first support substrate 217 and the secondsubstrate 227 be in contact with one another. In such embodiments, thefirst and second support substrates 217, 227 can share the samesubstrate, and a lid can be coupled to the spacer assembly 201. In someembodiments, the second acoustic wave device 274 can be flipped suchthat the third support substrate 276 is closer to the first acousticwave device 210 than the second support substrate 227.

As shown, for example, in FIG. 12D two or more different types ofacoustic wave devices can be stacked in an acoustic wave deviceassembly. In some embodiments, the single side solid acoustic mirrorstructure can enable more flexibility in frequency trimming as comparedto other structures of acoustic wave devices, such as the double sidesolid acoustic mirror structure. In some applications, the availabilityof the frequency trimming can significantly increase yield formanufacturing the acoustic wave device assembly. In some embodiments,the double side solid acoustic mirror structure can enable an acousticwave device assembly to have reduced vertical dimension as compared toother structures of acoustic wave devices, such as a single side solidacoustic mirror structure. Accordingly, by combining different types ofacoustic wave devices in an acoustic wave device assembly an optimalcharacteristics of the acoustic wave device assembly may be obtained.

FIG. 12E passivation is a schematic cross sectional side view of anacoustic wave device assembly 200 i according to an embodiment. Unlessotherwise noted components of the acoustic wave device assembly 200 ican be the same or similar to like components disclosed herein. Theacoustic wave device assembly 200 i is generally similar to the stackedacoustic wave device assembly 200 a shown in FIG. 11A. The acoustic wavedevice assembly 200 i can include a first acoustic wave device 210″ anda second acoustic wave device 220″. The first acoustic wave device 210″can include a first support substrate 217, first piezoelectric layer212, a first solid acoustic mirror 215 that is positioned between thefirst support substrate 217 and the first piezoelectric layer 212, afirst IDT electrode 214 over a surface of the first piezoelectric layer212, and a passivation layer 280. The second acoustic wave device 220″can include a second support substrate 227, a second piezoelectric layer222, a second solid acoustic mirror 225 that is positioned between thesecond support substrate 217 and the second piezoelectric layer 212, asecond IDT electrode 224 over a surface of the second piezoelectriclayer 212, and a passivation layer 282.

The passivation layer 280, 282 can protect the first and second IDTelectrodes 214, 224 against, for example, corrosion. A silicon nitride(SiN) layer or silicon dioxide (SiO₂) layer can be used as thepassivation layer.

Any suitable combination or selective combination of the examplevariations disclosed herein can made. For example, the variations shownin FIGS. 12A-12E can be combined, altered, or modified in accordancewith principles and advantages disclosed herein.

FIGS. 13A-13E show that the variations shown in FIGS. 12A-12E canimplement the first IDT electrode 234′ and the second IDT electrode 244′shown in FIG. 11D. FIGS. 13A-13E are schematic cross sectional sideviews of acoustic wave device assemblies 200 j, 200 k, 200 l, 200 m, 200n according to various embodiments. Unless otherwise noted components ofthe acoustic wave device assemblies 200 j, 200 k, 200 l, 200 m, 200 ncan be the same or similar to like components disclosed herein. Theacoustic wave device assemblies 200 j, 200 k include first and secondacoustic wave devices 230′, 340′. The acoustic wave device assembly 200Iincludes first and second acoustic wave devices 230″, 340″. The acousticwave device assembly 200 m includes first and second acoustic wavedevices 230′, 274′. The acoustic wave device assembly 200 m includesfirst and second acoustic wave devices 230′″, 240′″.

FIGS. 13F-13I show that the variations shown in FIGS. 12A-12D canimplement the first IDT electrode 254 and the second IDT electrode 264shown in FIG. 11D. FIGS. 13F-13I are schematic cross sectional sideviews of acoustic wave device assemblies 200 o, 200 p, 200 q, 200 raccording to various embodiments. Unless otherwise noted components ofthe acoustic wave device assemblies 200 o, 200 p, 200 q, 200 r can bethe same or similar to like components disclosed herein. The acousticwave device assemblies 200 o, 200 p include first and second acousticwave devices 250, 260. The acoustic wave device assembly 200 q includesfirst and second acoustic wave devices 250′, 260′. The acoustic wavedevice assembly 200 r includes first and second acoustic wave devices250, 274″.

Acoustic wave devices (or acoustic wave resonators) disclosed herein canbe implemented in a variety of different filter topologies. Examplefilter topologies include without limitation, ladder filters, latticefilters, hybrid ladder lattice filters, filters that include ladderstages and a multi-mode surface acoustic wave filter, and the like. Suchfilters can be band pass filters. In some other applications, suchfilters include band stop filters. In some instances, acoustic wavedevices disclosed herein can be implemented in filters with one or moreother types of resonators and/or with passive impedance elements, suchas one or more inductors and/or one or more capacitors. When two (ormore) acoustic wave devices are described as used in the same filtertopology, they can be part of the same stacked acoustic wave deviceassembly 200 as has been described with respect to FIGS. 11A to 13E inthe foregoing, or part of different stacked acoustic wave deviceassemblies 200, or can be provided as individually separated. Someexample filter topologies will now be discussed with reference to FIGS.14 to 16 . Any suitable combination of features of the filter topologiesof FIGS. 14 to 16 can be implemented together with each other and/orwith other filter topologies.

FIG. 14 is a schematic diagram of a ladder filter 300 that includes alaterally excited bulk acoustic wave resonator according to anembodiment and/or a leaky longitudinal surface acoustic wave resonatoraccording to an embodiment. The ladder filter 300 is an example topologythat can implement a band pass filter formed from acoustic waveresonators. In a band pass filter with a ladder filter topology, theshunt resonators can have lower resonant frequencies than the seriesresonators. The ladder filter 300 can be arranged to filter a radiofrequency signal. As illustrated, the ladder filter 300 includes seriesacoustic wave resonators R1 R3, R5, and R7 and shunt acoustic waveresonators R2, R4, R6, and R8 coupled between a first input/output portI/O1 and a second input/output port I/O2. Any suitable number of seriesacoustic wave resonators can be in included in a ladder filter. Anysuitable number of shunt acoustic wave resonators can be included in aladder filter.

One or more of the acoustic wave resonators of the ladder filter 300 caninclude a laterally excited bulk acoustic wave filter or a leakylongitudinal surface acoustic wave filter according to an embodiment. Incertain applications, all acoustic resonators of the ladder filter 300can be laterally excited bulk acoustic wave resonators or leakylongitudinal surface acoustic wave resonators in accordance with anysuitable principles and advantages disclosed herein. According to someapplications, the ladder filter 300 can include at least one laterallyexcited bulk acoustic wave device according to one embodiment and atleast one other laterally excited bulk acoustic wave device according toanother embodiment, and/or at least one leaky longitudinal surfaceacoustic wave device according to one embodiment and at least one otherleaky longitudinal surface acoustic wave device according to anotherembodiment. The eight laterally excited bulk acoustic wave devices R1-R8in FIG. 14 can be provided by four stacked acoustic wave deviceassemblies in each of which both acoustic wave devices are laterallyexcited bulk acoustic wave devices.

The first input/output port I/O1 can a transmit port and the secondinput/output port I/O2 can be an antenna port. Alternatively, firstinput/output port I/O1 can a receive port and the second input/outputport I/O2 can be an antenna port.

FIG. 15 is a schematic diagram of a lattice filter 310 that includes alaterally excited bulk acoustic wave resonator according to anembodiment and/or a leaky longitudinal surface acoustic wave deviceaccording to an embodiment. The lattice filter 310 is an exampletopology of a band pass filter formed from acoustic wave resonators. Thelattice filter 310 can be arranged to filter an RF signal. Asillustrated, the lattice filter 310 includes acoustic wave resonatorsRL1, RL2, RL3, and RL4. The acoustic wave resonators RL1 and RL2 areseries resonators. The acoustic wave resonators RL3 and RL4 are shuntresonators. The illustrated lattice filter 310 has a balanced input anda balanced output. One or more of the illustrated acoustic waveresonators RL1 to RL4 can be a laterally excited bulk acoustic waveresonator and/or a leaky longitudinal surface acoustic wave resonator inaccordance with any suitable principles and advantages disclosed herein.The four acoustic wave devices RL1-RL4 in FIG. 14 can be provided by twostacked acoustic wave device assemblies according to an embodiment.

FIG. 16 is a schematic diagram of a hybrid ladder and lattice filter 320that includes a laterally excited bulk acoustic wave resonator accordingto an embodiment. The illustrated hybrid ladder and lattice filter 320includes series acoustic resonators RL1, RL2, RH3, and RH4 and shuntacoustic resonators RL3, RL4, RH1, and RH2. The hybrid ladder andlattice filter 320 includes one or more laterally excited bulk acousticwave resonators and/or one or more leaky longitudinal surface acousticwave resonators in accordance with any suitable principles andadvantages disclosed herein. For example, the series resonators RL1,RL2, RH3, and RH4 and the shunt resonators RL3, RL4, RH1, and RH2 caneach be a laterally excited bulk acoustic wave resonator or a leakylongitudinal surface acoustic wave device according to an embodiment.The eight acoustic wave devices RH1-RH4, R1-RL4 in FIG. 16 can beprovided by four stacked acoustic wave device assemblies according to anembodiment.

According to certain applications, a laterally excited bulk acousticwave resonator or a leaky longitudinal surface acoustic wave resonatorcan be included in filter that also includes one or more inductors andone or more capacitors.

The laterally excited bulk acoustic wave resonators and/or leakylongitudinal surface acoustic wave resonators disclosed herein can beimplemented in a standalone filter and/or in a filter in any suitablemultiplexer. Such filters can be any suitable topology, such as anyfilter topology of FIGS. 24 to 26 . The filter can be a band pass filterarranged to filter a 4G LTE band and/or 5G NR band. Examples of astandalone filter and multiplexers will be discussed with reference toFIGS. 17A to 17E. Any suitable principles and advantages of thesefilters and/or multiplexers can be implemented together with each other.

FIG. 17A is schematic diagram of an acoustic wave filter 330. Theacoustic wave filter 330 is a band pass filter. The acoustic wave filter330 is arranged to filter a radio frequency. The acoustic wave filter330 includes one or more acoustic wave devices coupled between a firstinput/output port RF_IN and a second input/output port RF_OUT. Theacoustic wave filter 330 includes a laterally excited bulk acoustic waveresonator or a leaky longitudinal surface acoustic wave resonatoraccording to an embodiment.

FIG. 17B is a schematic diagram of a duplexer 332 that includes anacoustic wave filter according to an embodiment. The duplexer 332includes a first filter 330A and a second filter 330B coupled togetherat a common node COM. One of the filters of the duplexer 332 can be atransmit filter and the other of the filters of the duplexer 332 can bea receive filter. In some other instances, such as in a diversityreceive application, the duplexer 332 can include two receive filters.Alternatively, the duplexer 332 can include two transmit filters. Thecommon node COM can be an antenna node. The two acoustic wave filters330A, 330B can be part of the same stacked acoustic wave device assemblyaccording to an embodiment.

The first filter 330A is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 330A includes one or moreacoustic wave resonators coupled between a first radio frequency nodeRF1 and the common node COM. The first radio frequency node RF1 can be atransmit node or a receive node. The first filter 330A includes alaterally excited bulk acoustic wave resonator or a leaky longitudinalsurface acoustic wave resonator in accordance with any suitableprinciples and advantages disclosed herein.

The second filter 330B can be any suitable filter arranged to filter asecond radio frequency signal. The second filter 330B can be, forexample, an acoustic wave filter, an acoustic wave filter that includesa laterally exited bulk acoustic wave resonator, a leaky longitudinalsurface acoustic wave resonator, an LC filter, a hybrid acoustic wave LCfilter, or the like. The second filter 330B is coupled between a secondradio frequency node RF2 and the common node. The second radio frequencynode RF2 can be a transmit node or a receive node. The two acoustic wavefilters 330A, 330B can be part of the same stacked acoustic wave deviceassembly according to an embodiment.

Although example embodiments may be discussed with filters or duplexersfor illustrative purposes, any suitable principles and advantagesdisclosed herein can be implement in a multiplexer that includes aplurality of filters coupled together at a common node. Examples ofmultiplexers include but are not limited to a duplexer with two filterscoupled together at a common node, a triplexer with three filterscoupled together at a common node, a quadplexer with four filterscoupled together at a common node, a hexaplexer with six filters coupledtogether at a common node, an octoplexer with eight filters coupledtogether at a common node, or the like. Multiplexers can include filtershaving different passbands. Multiplexers can include any suitable numberof transmit filters and any suitable number of receive filters. Forexample, a multiplexer can include all receive filters, all transmitfilters, or one or more transmit filters and one or more receivefilters. One or more filters of a multiplexer can include any suitablenumber of laterally excited bulk acoustic wave devices. Each pair of anytwo filters may be provided as part of the same stacked acoustic wavedevice assembly according to an embodiment.

FIG. 17C is a schematic diagram of a multiplexer 334 that includes anacoustic wave filter according to an embodiment. The multiplexer 334includes a plurality of filters 330A to 330N coupled together at acommon node COM. The plurality of filters can include any suitablenumber of filters including, for example, 3 filters, 4 filters, 5filters, 6 filters, 7 filters, 8 filters, or more filters. Some or allof the plurality of acoustic wave filters can be acoustic wave filters.As illustrated, the filters 330A to 330N each have a fixed electricalconnection to the common node COM. This can be referred to as hardmultiplexing or fixed multiplexing. Filters have fixed electricalconnections to the common node in hard multiplexing applications. Anypair of acoustic wave filters 330A, 330B, . . . 330N can be provided byone stacked acoustic wave device assembly according to an embodiment.

The first filter 330A is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 330A can include one or moreacoustic wave devices coupled between a first radio frequency node RF1and the common node COM. Each pair of two acoustic wave devices can beimplemented by the same stacked acoustic wave device assembly accordingto an embodiment. The first radio frequency node RF1 can be a transmitnode or a receive node. The first filter 330A includes a laterallyexcited bulk acoustic wave resonator in accordance with any suitableprinciples and advantages disclosed herein. The other filter(s) of themultiplexer 334 can include one or more acoustic wave filters, one ormore acoustic wave filters that include a laterally excited bulkacoustic wave resonator, a leaky longitudinal surface acoustic wavedevice, one or more LC filters, one or more hybrid acoustic wave LCfilters, or any suitable combination thereof. The two acoustic wavefilters 330A, 330B can be part of the same stacked acoustic wave deviceassembly according to an embodiment.

FIG. 17D is a schematic diagram of a multiplexer 336 that includes anacoustic wave filter according to an embodiment. The multiplexer 336 islike the multiplexer 334 of FIG. 17C, except that the multiplexer 336implements switched multiplexing. In switched multiplexing, a filter iscoupled to a common node via a switch. In the multiplexer 336, theswitch 337A to 337N can selectively electrically connect respectivefilters 330A to 330N to the common node COM. For example, the switch337A can selectively electrically connect the first filter 330A thecommon node COM via the switch 337A. Any suitable number of the switches337A to 337N can electrically a respective filters 330A to 330N to thecommon node COM in a given state. Similarly, any suitable number of theswitches 337A to 337N can electrically isolate a respective filter 330Ato 330N to the common node COM in a given state. The functionality ofthe switches 337A to 337N can support various carrier aggregations. Anypair of acoustic wave filters 330A, 330B, . . . 330N can be provided byone stacked acoustic wave device assembly according to an embodiment.

FIG. 17E is a schematic diagram of a multiplexer 338 that includes anacoustic wave filter according to an embodiment. The multiplexer 338illustrates that a multiplexer can include any suitable combination ofhard multiplexed and switched multiplexed filters. One or more laterallyexcited bulk acoustic wave or leaky longitudinal surface acoustic wavedevice devices can be included in a filter that is hard multiplexed tothe common node of a multiplexer. Alternatively or additionally, one ormore laterally excited bulk acoustic wave devices or leaky longitudinalsurface acoustic wave devices can be included in a filter that is switchmultiplexed to the common node of a multiplexer. Any pair of twoacoustic wave devices can be provided by one stacked acoustic wavedevice assembly according to an embodiment.

The acoustic wave devices disclosed herein can be implemented in avariety of packaged modules. Some example packaged modules will now bedisclosed in which any suitable principles and advantages of theacoustic wave devices, acoustic wave components, or stacked acousticwave device assemblies disclosed herein can be implemented. The examplepackaged modules can include a package that encloses the illustratedcircuit elements. A module that includes a radio frequency component canbe referred to as a radio frequency module. The illustrated circuitelements can be disposed on a common packaging substrate. The packagingsubstrate can be a laminate substrate, for example. FIGS. 18 to 22 areschematic block diagrams of illustrative packaged modules according tocertain embodiments. Any suitable combination of features of thesepackaged modules can be implemented with each other. While duplexers areillustrated in the example packaged modules of FIGS. 19, 20, and 22 ,any other suitable multiplexer that includes a plurality of filterscoupled to a common node and/or standalone filter can be implementedinstead of one or more duplexers. For example, a quadplexer can beimplemented in certain applications. As another example, one or morefilters of a packaged module can be arranged as a transmit filter or areceive filter that is not included in a multiplexer.

FIG. 18 is a schematic diagram of a radio frequency module 340 thatincludes an acoustic wave component 342 according to an embodiment. Theillustrated radio frequency module 340 includes the acoustic wavecomponent 342 and other circuitry 343. The acoustic wave component 342can include one or more acoustic wave devices or stacked acoustic wavedevice assemblies in accordance with any suitable combination offeatures of the acoustic wave filters disclosed herein. The acousticwave component 342 can include an acoustic wave filter that includes aplurality of laterally excited bulk acoustic wave resonators or leakylongitudinal surface acoustic wave resonators, for example.

The acoustic wave component 342 shown in FIG. 18 includes one or moreacoustic wave devices 344 and terminals 345A and 345B. The one or moreacoustic wave devices 344 includes an acoustic wave device implementedin accordance with any suitable principles and advantages disclosedherein. The terminals 345A and 344B can serve, for example, as an inputcontact and an output contact. Although two terminals are illustrated,any suitable number of terminals can be implemented for a particularapplication. The acoustic wave component 342 and the other circuitry 343are on a common packaging substrate 346 in FIG. 18 . The packagesubstrate 346 can be a laminate substrate. The terminals 345A and 345Bcan be electrically connected to contacts 347A and 347B, respectively,on the packaging substrate 346 by way of electrical connectors 348A and348B, respectively. The electrical connectors 348A and 348B can be bumpsor wire bonds, for example.

The other circuitry 343 can include any suitable additional circuitry.For example, the other circuitry can include one or more radio frequencyamplifiers (e.g., one or more power amplifiers and/or one or more lownoise amplifiers), one or more radio frequency switches, one or moreadditional filters, one or more RF couplers, one or more delay lines,one or more phase shifters, the like, or any suitable combinationthereof. The other circuitry 343 can be electrically connected to theone or more acoustic wave devices 344. The radio frequency module 340can include one or more packaging structures to, for example, provideprotection and/or facilitate easier handling of the radio frequencymodule 340. Such a packaging structure can include an overmold structureformed over the packaging substrate 346. The overmold structure canencapsulate some or all of the components of the radio frequency module340.

FIG. 19 is a schematic block diagram of a module 350 that includesduplexers 351A to 351N and an antenna switch 352. One or more filters ofthe duplexers 351A to 351N can include an acoustic wave device or astacked acoustic wave device assembly in accordance with any suitableprinciples and advantages disclosed herein. Any suitable number ofduplexers 351A to 351N can be implemented. The antenna switch 352 canhave a number of throws corresponding to the number of duplexers 351A to351N. The antenna switch 352 can include one or more additional throwscoupled to one or more filters external to the module 350 and/or coupledto other circuitry. The antenna switch 352 can electrically couple aselected duplexer to an antenna port of the module 350.

FIG. 20 is a schematic block diagram of a module 360 that includes apower amplifier 362, a radio frequency switch 364, and duplexers 351A to351N according to an embodiment. The power amplifier 362 can amplify aradio frequency signal. The radio frequency switch 364 can be amulti-throw radio frequency switch. The radio frequency switch 364 canelectrically couple an output of the power amplifier 362 to a selectedtransmit filter of the duplexers 351A to 351N. One or more filters ofthe duplexers 351A to 351N can include an acoustic wave device orstacked acoustic wave device assembly in accordance with any suitableprinciples and advantages disclosed herein. Any suitable number ofduplexers 351A to 351N can be implemented. Any duplexer 351A to 351N canbe implemented using a stacked acoustic wave device assembly accordingto embodiments.

FIG. 21 is a schematic block diagram of a module 370 that includesfilters 372A to 372N, a radio frequency switch 374, and a low noiseamplifier 376 according to an embodiment. One or more filters of thefilters 372A to 372N can include any suitable number of acoustic wavedevices or stacked acoustic wave device assemblies in accordance withany suitable principles and advantages disclosed herein. Any suitablenumber of filters 372A to 372N can be implemented, for example by anynumber of stacked acoustic wave device assemblies. The illustratedfilters 372A to 372N are receive filters. In some embodiments (notillustrated), one or more of the filters 372A to 372N can be included ina multiplexer that also includes a transmit filter. The radio frequencyswitch 374 can be a multi-throw radio frequency switch. The radiofrequency switch 374 can electrically couple an output of a selectedfilter of filters 372A to 372N to the low noise amplifier 376. In someembodiments (not illustrated), a plurality of low noise amplifiers canbe implemented. The module 370 can include diversity receive features incertain applications.

FIG. 22 is a schematic diagram of a radio frequency module 380 thatincludes an acoustic wave filter or a stacked acoustic wave deviceassembly according to an embodiment. As illustrated, the radio frequencymodule 380 includes duplexers 351A to 351N, a power amplifier 362, aselect switch 364, and an antenna switch 352. Each duplexer 351A to 351Nmay be implemented using a stacked acoustic wave device assemblyaccording to embodiments. The radio frequency module 380 can include apackage that encloses the illustrated elements. The illustrated elementscan be disposed on a common packaging substrate 387. The packagingsubstrate 387 can be a laminate substrate, for example. A radiofrequency module that includes a power amplifier can be referred to as apower amplifier module. A radio frequency module can include a subset ofthe elements illustrated in FIG. 22 and/or additional elements. Theradio frequency module 380 may include any one of the acoustic wavefilters or stacked acoustic wave device assemblies in accordance withany suitable principles and advantages disclosed herein.

The duplexers 351A to 351N can each include two acoustic wave filterscoupled to a common node. For example, the two acoustic wave filters canbe a transmit filter and a receive filter. Each duplexer 351A to 351Ncan be implemented using one stacked acoustic wave device assembly. Asillustrated, the transmit filter and the receive filter can each be aband pass filter arranged to filter a radio frequency signal. One ormore of the transmit filters can include an acoustic wave device inaccordance with any suitable principles and advantages disclosed herein.Similarly, one or more of the receive filters can include an acousticwave device in accordance or a stacked acoustic wave device assemblywith any suitable principles and advantages disclosed herein. AlthoughFIG. 22 illustrates duplexers, any suitable principles and advantagesdisclosed herein can be implemented in other multiplexers (e.g.,quadplexers, hexaplexers, octoplexers, etc.) and/or in switch-plexersand/or with standalone filters.

The power amplifier 362 can amplify a radio frequency signal. Theillustrated switch 364 is a multi-throw radio frequency switch. Theswitch 364 can electrically couple an output of the power amplifier 362to a selected transmit filter of the transmit filters of the duplexers351A to 351N. In some instances, the switch 364 can electrically connectthe output of the power amplifier 362 to more than one of the transmitfilters. The antenna switch 352 can selectively couple a signal from oneor more of the duplexers 351A to 351N to an antenna port ANT. Theduplexers 351A to 351N can be associated with different frequency bandsand/or different modes of operation (e.g., different power modes,different signaling modes, etc.).

The acoustic wave devices disclosed herein can be implemented inwireless communication devices. FIG. 23 is a schematic block diagram ofa wireless communication device 390 that includes a filter or a stackedacoustic wave device assembly according to an embodiment. The wirelesscommunication device 390 can be a mobile device. The wirelesscommunication device 390 can be any suitable wireless communicationdevice. For instance, a wireless communication device 390 can be amobile phone, such as a smart phone. As illustrated, the wirelesscommunication device 390 includes a baseband system 391, a transceiver392, a front end system 393, antennas 394, a power management system395, a memory 396, a user interface 397, and a battery 398.

The wireless communication device 390 can be used communicate using awide variety of communications technologies, including, but not limitedto, 2G, 3G, 4G (including LTE, LTE-Advanced, and LTE-Advanced Pro), 5GNR, WLAN (for instance, WiFi), WPAN (for instance, Bluetooth andZigBee), WMAN (for instance, WiMax), and/or GPS technologies.

The transceiver 392 generates RF signals for transmission and processesincoming RF signals received from the antennas 394. Variousfunctionalities associated with the transmission and receiving of RFsignals can be achieved by one or more components that are collectivelyrepresented in FIG. 23 as the transceiver 392. In one example, separatecomponents (for instance, separate circuits or dies) can be provided forhandling certain types of RF signals.

The front end system 393 aids in conditioning signals transmitted toand/or received from the antennas 394. In the illustrated embodiment,the front end system 393 includes antenna tuning circuitry 400, poweramplifiers (PAs) 401, low noise amplifiers (LNAs) 402, filters 403,switches 404, and signal splitting/combining circuitry 405. However,other implementations are possible. The filters 403 can include one ormore acoustic wave filters that include any suitable number of laterallyexcited bulk acoustic wave devices in accordance with any suitableprinciples and advantages disclosed herein.

For example, the front end system 393 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals, or any suitable combination thereof.

In certain implementations, the wireless communication device 390supports carrier aggregation, thereby providing flexibility to increasepeak data rates. Carrier aggregation can be used for Frequency DivisionDuplexing (FDD) and/or Time Division Duplexing (TDD), and may be used toaggregate a plurality of carriers and/or channels. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

The antennas 394 can include antennas used for a wide variety of typesof communications. For example, the antennas 394 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 394 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The wireless communication device 390 can operate with beamforming incertain implementations. For example, the front end system 393 caninclude amplifiers having controllable gain and phase shifters havingcontrollable phase to provide beam formation and directivity fortransmission and/or reception of signals using the antennas 394. Forexample, in the context of signal transmission, the amplitude and phasesof the transmit signals provided to the antennas 394 are controlled suchthat radiated signals from the antennas 394 combine using constructiveand destructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction. In the context of signal reception, the amplitude andphases are controlled such that more signal energy is received when thesignal is arriving to the antennas 394 from a particular direction. Incertain implementations, the antennas 394 include one or more arrays ofantenna elements to enhance beamforming.

The baseband system 391 is coupled to the user interface 397 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 391 provides the transceiver 392with digital representations of transmit signals, which the transceiver392 processes to generate RF signals for transmission. The basebandsystem 391 also processes digital representations of received signalsprovided by the transceiver 392. As shown in FIG. 23 , the basebandsystem 391 is coupled to the memory 396 of facilitate operation of thewireless communication device 390.

The memory 396 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of thewireless communication device 390 and/or to provide storage of userinformation.

The power management system 395 provides a number of power managementfunctions of the wireless communication device 390. In certainimplementations, the power management system 395 includes a PA supplycontrol circuit that controls the supply voltages of the poweramplifiers 401. For example, the power management system 395 can beconfigured to change the supply voltage(s) provided to one or more ofthe power amplifiers 401 to improve efficiency, such as power addedefficiency (PAE).

As shown in FIG. 23 , the power management system 395 receives a batteryvoltage from the battery 398. The battery 398 can be any suitablebattery for use in the wireless communication device 390, including, forexample, a lithium-ion battery.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includesexample embodiments, the teachings described herein can be applied to avariety of structures. Any of the principles and advantages discussedherein can be implemented in association with RF circuits configured toprocess signals having a frequency in a range from about 30 kHz to 300GHz, such as in a frequency range from about 400 MHz to 25 GHz.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, radiofrequency filter die, uplink wireless communication devices, wirelesscommunication infrastructure, electronic test equipment, etc. Examplesof the electronic devices can include, but are not limited to, a mobilephone such as a smart phone, a wearable computing device such as a smartwatch or an ear piece, a telephone, a television, a computer monitor, acomputer, a modem, a hand-held computer, a laptop computer, a tabletcomputer, a microwave, a refrigerator, a vehicular electronics systemsuch as an automotive electronics system, a robot such as an industrialrobot, an Internet of things device, a stereo system, a digital musicplayer, a radio, a camera such as a digital camera, a portable memorychip, a home appliance such as a washer or a dryer, a peripheral device,a wrist watch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context indicates otherwise, throughout the description andthe claims, the words “comprise,” “comprising,” “include,” “including”and the like are to generally be construed in an inclusive sense, asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” Conditional language usedherein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,”“for example,” “such as” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. The word “coupled”, as generally used herein, refers to two ormore elements that may be either directly coupled, or coupled by way ofone or more intermediate elements. Likewise, the word “connected”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Additionally, the words “herein,” “above,” “below,” and wordsof similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel filters, multiplexer,devices, modules, wireless communication devices, apparatus, methods,and systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in theform of the filters, multiplexer, devices, modules, wirelesscommunication devices, apparatus, methods, and systems described hereinmay be made without departing from the spirit of the disclosure. Forexample, while blocks are presented in a given arrangement, alternativeembodiments may perform similar functionalities with differentcomponents and/or circuit topologies, and some blocks may be deleted,moved, added, subdivided, combined, and/or modified. Each of theseblocks may be implemented in a variety of different ways. Any suitablecombination of the elements and/or acts of the various embodimentsdescribed above can be combined to provide further embodiments. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosure.

What is claimed is:
 1. An acoustic wave device assembly comprising: afirst acoustic wave device including a first substrate, a firstpiezoelectric layer, a first solid acoustic mirror disposed between thefirst substrate and the first piezoelectric layer, and a firstinterdigital transducer electrode embedded in the piezoelectric layer;and a second acoustic wave device including a second substrate, a secondpiezoelectric layer, a second solid acoustic mirror disposed between thesecond substrate and the second piezoelectric layer, and a secondinterdigital transducer electrode in contact with the secondpiezoelectric layer, the second acoustic wave device being stacked overthe first acoustic wave device, the first acoustic wave device and thesecond acoustic wave device being spaced by a spacer assembly such thata cavity is formed between the first acoustic wave device and the secondacoustic wave device.
 2. The acoustic wave device assembly of claim 1wherein the second interdigital transducer is embedded in the secondpiezoelectric layer.
 3. The acoustic wave device assembly of claim 1wherein the first interdigital transducer electrode is completelyembedded in the first piezoelectric layer such that the firstinterdigital transducer electrode is positioned closer to the cavitythan to the first solid acoustic mirror.
 4. The acoustic wave deviceassembly of claim 1 wherein the first solid acoustic mirror includesalternating low impedance layers and high impedance layers that has ahigher impedance than the low impedance layers of first solid acousticmirror.
 5. The acoustic wave device assembly of claim 4 wherein thesecond solid acoustic mirror includes alternating low impedance layersand high impedance layers that has a higher impedance than the lowimpedance layers of second solid acoustic mirror.
 6. The acoustic wavedevice assembly of claim 5 wherein the low impedance layers of the firstsolid acoustic mirror and the low impedance layers of the second solidacoustic mirror have different thicknesses.
 7. The acoustic wave deviceassembly of claim 1 wherein the first piezoelectric layer and the secondpiezoelectric layer are positioned between the first and secondsubstrates.
 8. The acoustic wave device assembly of claim 1 wherein thesecond substrate is disposed between the first and second piezoelectriclayers.
 9. The acoustic wave device assembly of claim 1 wherein at leastone of the first acoustic wave device or the second acoustic wave deviceis a laterally excited bulk acoustic wave resonator.
 10. The acousticwave device assembly of claim 1 wherein at least one of the firstacoustic wave device or the second acoustic wave device is a leakylongitudinal surface acoustic wave resonator.
 11. The acoustic wavedevice assembly of claim 1 wherein the first acoustic wave device has asingle mirror structure and the second acoustic wave device has a doublemirror structure.
 12. An acoustic wave device assembly comprising: afirst acoustic wave device including a first substrate, a firstpiezoelectric layer having a first portion and a second portion, a firstsolid acoustic mirror disposed between the first substrate and the firstpiezoelectric layer, and a first interdigital transducer electrode onthe first portion of the first piezoelectric layer and covered by thesecond portion of the first piezoelectric layer; and a second acousticwave device including a second substrate, a second piezoelectric layer,a second solid acoustic mirror disposed between the second substrate andthe second piezoelectric layer, and a second interdigital transducerelectrode in contact with the second piezoelectric layer, the secondacoustic wave device being stacked over the first acoustic wave device,the first acoustic wave device and the second acoustic wave device beingspaced by a spacer assembly such that a cavity is formed between thefirst acoustic wave device and the second acoustic wave device.
 13. Theacoustic wave device assembly of claim 12 wherein the secondinterdigital transducer is embedded in the second piezoelectric layer.14. The acoustic wave device assembly of claim 12 wherein a thickness ofthe first portion of the first piezoelectric layer is greater than athickness of the second portion of the second piezoelectric layer. 15.The acoustic wave device assembly of claim 12 wherein the first solidacoustic mirror includes alternating low impedance layers and highimpedance layers that has a higher impedance than the low impedancelayers of first solid acoustic mirror.
 16. The acoustic wave deviceassembly of claim 15 wherein the second solid acoustic mirror includesalternating low impedance layers and high impedance layers that has ahigher impedance than the low impedance layers of second solid acousticmirror.
 17. The acoustic wave device assembly of claim 16 wherein thelow impedance layers of the first solid acoustic mirror and the lowimpedance layers of the second solid acoustic mirror have differentthicknesses.
 18. The acoustic wave device assembly of claim 12 whereinthe first piezoelectric layer and the second piezoelectric layer arepositioned between the first and second substrates.
 19. The acousticwave device assembly of claim 12 wherein the second substrate isdisposed between the first and second piezoelectric layers.
 20. Theacoustic wave device assembly of claim 12 wherein the first acousticwave device has a single mirror structure and the second acoustic wavedevice has a double mirror structure.